refractive index experiment equipment

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• Make That Invisible! Refractive Index Matching

Hands-on Activity Make That Invisible! Refractive Index Matching

Grade Level: 11 (9-12)

(can be split into four 50-minute sessions)

This activity also requires some non-expendable lab supplies and equipment that are all reusable if properly stored after the activity; see the Materials List for details.

Group Size: 4

Activity Dependency: None

Subject Areas: Physics

NGSS Performance Expectations:

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Refractive index is a fundamental optical property of materials, and knowing the accurate value of a material's refractive index enables us to predict the angle that light is bent as it passes through the material, which is important in many real-world applications. Chemical, environmental and biomedical engineers take advantage of refractive index matching to minimize (if not remove) multiple scattering when capturing images to study the properties and behavior of micro- and nano-sized particles (such as bacterial and colloidal systems). Optical engineers use accurate measurements of refractive index to design optical instrument components such as lenses, microscopes, telescopes as well as other equipment that utilize the properties of light. Mechanical engineers must know the refractive index of fluids and other materials to build efficient and affordable machines. These examples illustrate the importance of knowing and understanding the concept of refractive index. Numerous methods and modern instruments are available to accurately measure the refractive index of various materials.

After this activity, students should be able to:

• Determine the relationship of the angle of incidence and the angle of refraction between two different media.
• Measure the refractive index of a given liquid using Snell's law.
• Determine the refractive index of an unknown material using percent light transmission.

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Ngss: next generation science standards - science.

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For the teacher-led class demonstration:

• Disappearing Glass Demo Instructions
• two 500-ml clear glass beakers
• glycerin (or vegetable oil, such as Wesson; glycerin is preferred; see note below)
• 2 Pyrex stirring rods, such as the 12-inch clear glass stir rod available for $1.75 each at The Science Company website at https://www.sciencecompany.com/Clear-Glass-Stir-Rod-12-inch-P17256.aspx

Each group needs:

• poster board and writing utensils (or a small white board and a dry erase marker)
• Refractive Index Lab Worksheet
• (optional, for activity extension assignment) Refractive Index Application Research Questions

For Part 1, each group needs:

• laser pointer
• print out of a polar graph; such as the example graphs found at the University of South Florida's Florida Center for Instructional Technology ClipArtETC website at http://etc.usf.edu/clipart/43000/43018/polar_24-4l_43018.htm
• (optional but recommended) plastic sheet protector to protect the paper polar graph from spills
• semicircular hollow acrylic block, 12 cm diameter x 2.5 cm high, available (part# RCSC01) at Nova-Tech International at http://www.novatech-usa.com/RCSC01
• ~50 ml water
• ~50 ml glycerin (or vegetable oil, such as Wesson), such as ACS grade, 4-liter bottle of glycerin (catalog # S25342D) from Fischer at https://www.fishersci.com/shop/products/glycerin-4l-acs-grade/s25342d ; glycerin is preferred because it is the same color as water so students will not realize at first that the two liquids are different, and it is soluble in water, making clean-up easier

For Part 2, each group needs:

• LED lights/semiconductors (matching the color of the laser used), such as the LED semiconductors from Sargent Welch for a pack of five at https://sargentwelch.com/store/product/8887114/led-semiconductors
• 4 containers (cuvettes are preferred, but small test tubes also work)
• ~6 ml water
• ~6 ml glycerin (or vegetable oil, such as Wesson)
• 2 Pyrex glass tubes (~6 cm in length each) that fit in the sample container, as shown in Figure 2; such as "Rod, glass, Pyrex, 3 mm OD (outer diameter)," catalog # 239430, page 193 in University of Houston's Research Stores 2013 Catalog, for ~$1 per piece (~1.5 meter) at http://researchstores.nsm.uh.edu/catalog , Pyrex brand is necessary to get the desired results
• sample container rack or holder to securely hold vials of four samples, such as the one shown in Figure 2 made with cardboard, clear tape and two packing foam pieces
• electronic breadboard and electrical wire (optional but recommended to ensure the stability of the detector), such as the five mini solderless prototype breadboards with 170 tiepoints available for $6.67 at http://www.ebay.com/itm/5x-Transparent-Mini-Solderless-Prototype-Breadboard-170-Tie-points-for-Arduino-/231242048856?pt=LH_DefaultDomain_0&hash=item35d719a558 or www.amazon.com.

To share with the entire class:

• (optional but recommended if available) lux meter, to verify the reliability of the results from the homemade LED-multimeter light intensity detector; such as Mastech's light meter LX1010B, 50,000 Lux Luxmeter with LCD display for $15 (MSRP $50) at https://www.amazon.com/Light-Meter-LX1010B-Luxmeter-display/dp/B000JWUT6O

Student are expected to know:

• The basic properties of light, such as reflection, refraction, absorption, transmission and scattering.
• How to plot data points and determine the slope from the graph.
• The basic trigonometry (that is, the use of sine) for the calculation of refractive index using Snell's law.

(In advance, prepare to conduct a class demonstration, using the Disappearing Glass Demo Instructions as a guide, so the setup looks like Figure 1, with a stirring rod submerged in a beaker of water [left] and a stirring rod submerged in glycerin [right]. Write the challenge question on the classroom board. Then start by asking students the pre-assessment discussion questions, as described in the Assessment section. Then divide the class into groups of four and give each group a poster paper or small white board to write down its answers.)

What is the difference between transparent and invisible materials? (Listen to student answers.) Transparent material permits light to pass through it so that objects behind can be directly seen but the material itself is still visible to the naked eye. On the other hand, invisible material allows light to pass through as well, but it is not visible to our eyes.

Today, this is our challenge question : How can you make half of this stirring rod invisible without breaking it?

(Let students brainstorm and write down their final answers. Have each group share its answer and explain why. Summarize the answers on the classroom board.)

Let me show you one way of making half of the stirring rod disappear. (Demonstrate how to make half of the stirring rod disappear using two beakers, one with water and one with liquid glycerin.) What do you observe? (Students see examples of transparent and invisible materials, noticing that part of the rod submerged in glycerin appears to be invisible!)

(Expect some students to be fascinated. Others may have seen the demo but do not know the science behind it. Others may not believe it and examine the demo more carefully. Let students think about it and explore it for a few minutes. Then explain it.) If two materials have exactly the same refractive index (n), you cannot see the difference between the materials. Water has an n =1.33 while glycerin has n =1.47. A Pyrex stirring rod has n =1.47.

Light is very important in our lives. It travels in waves and has several unique properties—reflection, refraction, absorption, transmission and scattering. Light is the reason that we can see everything around us. However, have you ever thought that the unique properties of light could enable us to make something disappear? Before we get into making something "invisible," it is important for us to refresh our memories on what we mean by the refraction of light.

(Either introduce or review the concept of refraction.) Refraction is the bending of light as it passes from one medium to another. This behavior occurs because light changes speed when it travels into a different medium. Since light is used in a lot of research in science and engineering, it is important know how much light is refracting (or how much it changes its speed) in a given medium. Refractive index is one of the light optical properties that can be used to study the bending of light.

where c is the speed of light in a vacuum (3.0 x 10 8 m/s) and v is the speed of light in a certain medium. In other words, n is simply a way to know the speed of light in a medium relative to its speed in a vacuum. Based on current knowledge, we know of nothing faster than the speed of light in a vacuum.

(Give students a chance to think about their answers and then share what they are thinking).

For Part 1 of today's activity, we are going to use Snell's law to determine the index of refraction of an unknown liquid. A semi-circular hollow block is the container of your unknown liquid and you are going to change the angle of incidence of the laser beam at 5 o increments. Our first medium is the liquid and the second medium is the air. We will measure and record the angle of refraction in air. Then we will use the following relationship to determine the refractive index of the liquid ( n 1 ).

Snell's law is:

n 1 sinθ 1 = n 2 sinθ 2

If the second medium is air, we can assume that n 2 = 1:

n 1 sinθ 1 = sinθ 2

x = sin θ 1

n 1 sinθ 1 = sinθ 2 becomes y=n 1 x

Once you plot your data and the slope is determined, you can predict the identity of your unknown sample by referring to a list of known refractive indices of materials (Table 1).

Part 2 of the activity involves the refractive index matching of a material (a Pyrex glass tube) with two different liquids (water and glycerin). Refractive index matching is used by science and engineering researchers, such as in the analysis of colloidal system using imaging. The study of colloidal particle behavior has been important in the development of efficient and eco-friendly solutions to many energy and environmental challenges such as enhanced oil recovery, flow assurance, water management, and clean and efficient engines. Observing these systems in a micro- or nano-scale dimension using microscopes is not easy since they usually scatter light in all direction because the particles are so close to each other. Too much scattering makes the microscopic images blurry and unclear. (One way to minimize this is to reduce the concentration of the particles in a medium. However, lowering the concentration can reduce the signal being detected to observe the particles.) If the particles and the solvent have the same refractive index, light scattering is not a problem. Thus, refractive index matching is a significant tool enabling researchers to better observe what happens in experiments.

Refractive index matching is tested by determining the percent light transmission. The refractive index of the glass tube is matched to the refractive index of two different liquids. Recall what you observed in the "disappearing glass" demo. The stirring rod submerged in glycerin appeared to be invisible! In theory, if two materials have exactly the same refractive index, the light passes through without any (or minimal) scattering or refraction. The light travels straight because it cannot detect any difference in the two materials, hence the speed of the travelling light does not change (bend). Related to this, the higher the percent transmission of light in the sample with a glass tube in a liquid, we can assume that the glass tube has the same or close n of that liquid. In this activity, we will use an inexpensive and easy-to-build homemade detector for measuring the light intensity (in milliwatts).

Before the Activity

• Set up activity stations around the room with prepared samples for each team. The sample setup is shown in Figure 2, and an example station is shown in Figure 8. At each station, you may want to do steps 1 and 2 of Part 1 in advance of students arriving to conduct the activity.
• To ensure accurate data collection for Part 1, use clear tape to secure the semi-circular hollow block on the center of the polar graph. This minimizes movement of the block. Refer to Figures 5 and 7.
• For Part 2, set up the LED-multimeter detector as shown in Figure 6.
• If a lux meter is available, refer to the Refractive Index Lab Worksheet (Part 2, Analysis question #2) for information about the setup. This optional setup replaces the LED-multimeter detector with the lux meter. The percent transmission may not be the same since you are detecting light intensity in different units, but the trend will be similar.

With the Students—Part 1: Refractive Index Using a Hollow Cell

• Assign each group an "unknown" liquid. (Since students do not know that only samples of water and glycerin are available, give half of the class water and the other half glycerin.)
• Place the hollow semi-circular acrylic block filled with the group's assigned liquid at the center of the polar graph, as shown in Figure 4. If the polar graph is not protected by a plastic sheet, be careful not to get the paper wet!
• Use clear tape to secure the block to the graph. (Steps 1 and 2 may have already been done by the teacher.)
• Make sure that the laser pointer is working and lay it on the table so that the laser beam passes across the polar graph paper lying on the tabletop.
• Starting with the 0 o angle of incidence from normal (the line that is perpendicular to the flat edge of the block), rotate the graph paper at 5 o increments until the refracted ray totally disappears. (Refer to the setup in Figures 5 and 7.)
• Continue to change the angle of incidence by rotating the graph paper with the block, making sure that the light is always passing through the center point of the polar graph.
• Each time, record the angle of incidence ( θ 1 ) and angle of refraction ( θ 2 ).
• Take note of the angle at which the refracted ray totally disappears. This is called the total internal reflection. Teacher note: The critical angle (start of the total internal reflection) of light passing through water and air is 48.8° and for glycerin is 42.9°.
• Plot your data in terms of sin θ 2 vs. sin θ 1 . Determine the slope, which is the average refractive index. (Note: Recall Snell's law; n air = 1.00).

With the Students—Part 2. Refractive Index Matching Using Percent Light Transmission Measurement

• Your goal is to approximate the index of refraction of the glass tube based on the percent light transmission using a LED light and multimeter as the detector .

• Turn on the laser and the multimeter. Make sure that the laser beam is passing through the LED light. The light from the laser is converted to an electric signal that is read by the multimeter. Adjust the laser position and light height until you can detect the maximum signal in volts (V). Light intensity is directly proportional to the voltage you are reading. The LED light has a maximum output of ~1.0 V. After this step, DO NOT MOVE the laser or the detector while gathering data. Misalignment may give different results.
• Put the W1 sample container in between the laser and detector. Make sure the light is passing through the center of the sample container and the LED light.
• Determine the light intensity (in volts) after the laser passes through the sample. Record your data.
• Repeat steps 3-5 for samples W2, G1 and G2, recording the data.
• Calculate the percent transmission of light using the equation provided in Figure 8.
• Determine the refractive index of the glass tube based from the known data. For teacher reference, two methods are described below.

Method 1: Refractive Index Matching: Based on the percent light intensity equation, I is the light intensity that the multimeter is reading with the liquid and glass tube, while I o is the reading with pure liquid. If the glass tube has the same refractive index as the liquid in which it is submerged, the light passes through it without any refraction or scattering; thus, its percent light intensity is almost 100%. This method is commonly called "refractive index matching" and is typically used in situations in which it is hard to measure the refractive index of a certain substance, such as colloidal and bacterial systems.

Method 2: Another way to determine the refractive index is by using two sample containers, each with a different liquid. Measure the light intensity after the light passes through the container with liquid only. Then, submerge the Pyrex glass tube, then measure the light intensity passing through the sample container (now with glass tube and liquid). Follow with the same equation.

• Conclude the activity by having students answer the three lab reflection questions. Then collect the completed lab worksheets. If time permits, have students research and present to the rest of the class examples of real-world applications of refractive index applications used in science and engineering, as described in the Activity Extensions section.

absorption: A process in which light (energy) is transferred to a medium in which it is passing through.

angle of incidence: The angle measured between the normal and the incident light.

angle of refraction: The angle measured between the normal and the refracted light.

colloidal system: A system in which fine particles are dispersed within a continuous medium. A colloidal system may be solid, liquid or gas.

detector: A device that recovers or measures information.

normal: An imaginary line perpendicular to a surface.

reflection: The bouncing of light when it strikes a boundary between different media through which it cannot pass.

refraction: The bending of light as it passes from one medium to another.

refractive index: A number (optical property) that describes how light propagates through a medium.

scattering: The dispersal of rays of light when the light reflects from an unsmooth surface.

transmission: When light passes through a material and is not absorbed by that material.

Pre-Activity Assessment

Discussion Questions: To help students recall the common behaviors of light, give student pairs some time to discuss answers to the following questions. After the allotted time, have groups share their answers with the rest of the class. Answers to the following example questions are provided in the Pre-Activity Discussion Questions Answer Key .

• What is light?
• Light has the following behaviors when it is interacting with a certain boundary: reflection, refraction, absorption, transmission and scattering. For each, draw an example and use arrows to show how the light behaves.
• What is the difference between transparent and invisible?

Activity Embedded Assessment

Worksheets: During the course of the activity, have students complete the Refractive Index Lab Worksheet to show their understanding of the material as well as participation.

Post-Activity Assessment

Reflection Questions: At activity end, have students answer the three lab reflection summary questions and then turn in their completed lab worksheets. Review their answers to assess what they learned in the activity.

Safety Issues

• To keep the laser pointer from being pointed at people's eyes, use masking tape to secure the laser pointer in the setups before the activity begins.
• To prevent breakage and spills, place the activity glasses and liquids in a secure rack or container, such as the one shown in Figure 2 made from cardboard, tape and foam.

For Part 1, make sure that 1) the laser beam passes through the polar graph so students can see the incident and refracted beam clearly, 2) the light passes through the center point of the graph, and 3) the block is at the center of the polar graph.

For Part 2, make sure the LED-multimeter detector is stable during data collection. Moving any part of the detector after step 2 of Part 2 may give erroneous results. The electronic breadboard is helpful to avoid moving any detector part during the activity.

Knowing the refractive index of a material enables us to predict the angle that light is bent as it passes through the material, which is important in many real-world applications, such as the imaging of nano-sized particles by minimizing the scattering due to refraction, as well as the design of optical instruments and equipment that use light. Assign student teams to research real-world applications of refractive index matching in science and engineering. Hand out the Refractive Index Application Research Questions as a guide for their research. Give each group five minutes to present what they have researched in class in the form of a PowerPoint and/or poster presentations. Note: With so many applications to research, guide student teams to focus on one application as their topic, so as to not be overwhelmed with too much information.

For more information about total internal reflection (TIR):

• Applications of total internal reflection http://regentsprep.org/Regents/physics/phys04/captotint/
• Fiber Optic Cables: How They Work (5:35 minute video) https://www.youtube.com/watch?v=0MwMkBET_5I

Students learn about the basic properties of light and how light interacts with objects. They are introduced to the additive and subtractive color systems, and the phenomena of refraction. Students further explore the differences between the additive and subtractive color systems via predictions, ob...

Students learn about the science and math that explain light behavior, which engineers have exploited to create sunglasses. They examine tinted and polarized lenses, learn about light polarization, transmission, reflection, intensity, attenuation, and how different mediums reduce the intensities of ...

Contributors

Supporting program, acknowledgements.

Developed by the University of Houston's College of Engineering under National Science Foundation RET grant number 1130006. However, these contents do not necessarily represent the policies of the NSF and you should not assume endorsement by the federal government.

Last modified: December 11, 2020

Reflection and Refraction • EX-9987

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Student experiment exploring Snell’s Law and the Law of Reflection.

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Product Summary

Students experimentally derive the Law of Reflection for curved and flat mirrors. Snell’s Law is explored and the index of refraction for a piece of acrylic material is found.

PASCO Advantage:  Students trace the rays on the provided templates and make angle measurements directly from their drawing. This reinforces the connection between the real rays they can see in the lab and the type of ray diagrams seen in the classroom.

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Reflection and refraction.

• Index of Refraction

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15. Measurement of the refractive index of a material

rectangular glass or perspex block

ray box or optics lamp 1 cylindrical lens 1 single slit

power supply

A4 plain white paper

shaded or darkened conditions

Measuring the Refractive Index of Liquid at a Defined Wavelength

Introduction: Measuring the Refractive Index of Liquid at a Defined Wavelength

Theories behind the sensor

The refractive index of a liquid is an indirect measure of its dielectric constant and composition. For a pure substance, the refractive index is a tabulated physico-chemical parameter. This technique can therefore be used to identify a pure product. For formulations, measuring the index allows the concentration of a species to be quantified, for example the amount of sugar.

The refractive index is measured with a refractometer, which actually operates by measuring the limiting angle of refraction [Фl]. This angle indicates the point at which a light beam incident on a translucent surface of index [n] is no longer able to cross the surface, and instead is reflected, leading to a mirror effect in accordance with Snell's law.

Step 1: Components

Our designed diffractometer functions similarly to this raindrop sensor [1]. To analyze liquid samples, a laser beam with a wavelength of 650 nm is directed onto the liquid surface. The reflected beam intensity is measured by a photo detector. A particular shape is required to achieve an incident angle close to 45°:

To assemble the equipment, the following items are required:

• 2 M3 screws with a minimum length of 15 mm;
• 4 M3 washers;
• A piece of Cristal polystyrene (CD case) with L = 15, l = 10, and e = 0.8.
• The setup includes a mirror made of Crystal polystyrene coated with an aluminum foil (aluminum foil for food cooking application) dimensions L = 35, l = 10, and thickness e=0.8.
• A red diode laser (650 nm),
• A photodetector,
• And 2 parts that have been printed in PLA using a 3D printer.

The two symmetrical PLA components we design have the following dimensions: 

The middle of the trapezoidal cavity, with a depth of 5mm, follows the (h,2h,4h) rule mentioned earlier. The shape is rounded through chamfering. A vertical element with a height of 6.5mm and a thickness of 1mm is used to separate the two compartments, one for the transmitter (laser) and the other for the receiver (photodetector) and then prevent light interfering. The mirror is placed on the larger base while the polystyrene window is on the smaller base. The latter has a housing of 6.5mm diameter to hold the liquid to be measured. The laser and photodetector are housed in cylinders with a 6.5 mm entrance diameter and a 5.5 mm exit diameter. There are two 3.2mm holes for M3 screws, and the component's base has a 1mm thickness. 

Step 2: Assembling

The assembly is uncomplicated and can be completed in 4 steps : 

1) Two 8mm wide strips are cut from a CD cover made of Cristal polystyrene, a material known for its transparency, rigidity and resistance to solvents. One strip is adjusted to a length of 35mm and covered and glued with food grade aluminium foil to form a mirror. The second strip is adjusted to a length of 15mm and will function as a measurement window;

2) Adjust the mirror in the designated housing, taking care not to damage it. It is recommended to glue this element with cyanoacrylate glue (Superglue) to ensure its fixation. Wait for the glue to dry completely before proceeding with the assembly;

3) Place the laser diode, photodetector, and Crystal polystyrene window in their respective housing without immobilising them with glue. Consistency in replacement of the window is key in this device. The Crystal polystyrene window may require replacement with a new or alternative transparent material depending on varying needs, wear, and the liquids being tested. For the laser, it may be beneficial to measure the refractive index at a wavelength that differs from the 650 nm wavelength detailed in this presentation;

4) The assembly is fastened using two M3 screws, along with corresponding washers and nuts. For ease of disassembly, it is recommended that the simple nuts are replaced with wing nuts.

Attachments

Step 3: Electronics

The electronic enables the reflection to be converted into an electrical signal that can be used to measure the refractive index. A photodiode transforms light into electric current [i]. The output light intensity [iphoto] is determined by the input optical power [Ev] according to a power function [β]. When the photodiode receives illumination, it behaves like an ideal current source whose intensity is connected to the number of photons that arrive on the active surface.

Measuring light intensity is not a simple task. It involves assembling a circuit that links the measured light intensity to the corresponding voltage. A resistor [R PHD ] is used to insert a photodiode into reverse mode. The resistor allows the conversion of current produced by the photodiode into a voltage that an operational amplifier can measure.

The laser operates with the protection of resistor [R1], which limits the current passing through it. The operational amplifier would function properly without the presence of the capacitance [C1 of 4700pF]. However, it is better not to leave an AOP input without a signal if the photodiode is exposed to low light. Hence, capacitance [C1] serves its purpose. On the other hand, the inclusion of resistor [R2] allows for the construction of a low-pass filter with a cut-off frequency of around 500 Hz, thus eliminating the noise that could give us unwanted parasitic detections on the analogue output [Sig A0].

Step 4: References

[1] Gérard Villemin : http://villemin.gerard.free.fr/aGeneral/Transport/Pluie.htm

[2] Refractive index. Info : https://refractiveindex.info/?shelf=organic&book=acetone&page=Rheims

Component parts : Refractive index device, R1 = 330 Ω, RV2 = 100 kΩ, R3= 1 kΩ, R4= 10 kΩ, C1 = 4.7nF, 2 AOP = LM 393

Further Reading : « 100 Sensors In Action, Electronic For Chemists » - Gérard Bacquet- SciencExpert Edition - 2024

Step 5: Acknowledgment

Thanks to tengamari46 15 who pointed out an inconsistency in the schematic

Index of Refraction: Glass To use ray sightings to calculate the index of refraction of glass. to calculate the experimental index of refraction for glass based on the angle data for each interface. sin(θ ) = n sin(θ ) = 1.0 =  sin(θ )/sin(θ ) top interface bottom interface Measure in cm the length of the path followed by the light through the glass plate.  Calculate the average speed of light (in m/sec) through glass using your average experimental index of refraction.  Calculate the time required for the light to pass through the glass plate.  Copyright © 1997-2024 All rights reserved. Application Programmer     Mark Acton We apologize for the inconvenience... To ensure we keep this website safe, please can you confirm you are a human by ticking the box below. If you are unable to complete the above request please contact us using the below link, providing a screenshot of your experience. https://ioppublishing.org/contacts/ Waves And Optics Determination of the refractive index of a glass block Related documents. Add this document to collection(s) You can add this document to your study collection(s) Add this document to saved You can add this document to your saved list Suggest us how to improve StudyLib (For complaints, use another form ) Input it if you want to receive answer Refraction of Light ( CIE IGCSE Physics ) Revision note. Ray diagrams for refraction The angle of the wave approaching the boundary is called the angle of incidence (i) The angle of the wave leaving the boundary is called the angle of refraction (r) An incident ray has an arrow pointing towards the boundary A refracted ray has an arrow pointing away from the boundary The angles of incidence and refraction are usually labelled i and r respectively Refraction ray diagram A ray diagram for light refracting at a boundary, showing the normal, angle of incidence and angle of refraction Refraction of light At the boundary, the rays of light change  direction This change in direction depends on the difference in   density   between the two media: From   less dense to more dense   (e.g air to glass), light bends   towards   the normal From   more dense to less dense   (e.g. glass to air), light bends   away   from the normal When passing along the   normal   (perpendicular) the light   does not bend   at all The refracted ray at the first boundary becomes the incident ray at the second boundary Refraction diagram of light from air through a glass block How to construct a ray diagram showing the refraction of light as it passes through a rectangular block When light passes into a denser substance, the waves will slow down ; hence, they bend towards the normal Different frequencies account for different colours of light (red has a low frequency, whilst blue has a high frequency) When light refracts, it does not change colour (think of a pencil in a glass of water), therefore, the frequency does not change Practice drawing refraction diagrams as much as you can! It's very important to remember which way the light bends when it crosses a boundary: As the light enters the block it bends towards the normal line Remember: Enters Towards When it leaves the block it bends away from the normal line Remember: Leaves Away You only need to know about light passing through the boundaries between two media. Investigating Refraction Aims of the experiment. To investigate the refraction of light using rectangular blocks, semi-circular blocks and triangular prisms Independent variable = shape of the block Dependent variable = angle of refraction Width of the light beam Same frequency / wavelength of the light Equipment list Ray box To provide a narrow beam of light that can be easily refracted Protractor To measure the angles of incidence and refraction Sheet of paper To mark the lines indicating the incident and refracted rays Pencil To draw the incident and refracted ray lines onto the paper Ruler To draw the incident and refracted ray lines onto the paper Perspex blocks (rectangular, semi-circular & prism) To refract the light beam Protractor = 1° Ruler = 1 mm Refraction diagram for equipment Diagram showing a ray box alongside three different-shaped glass blocks Refraction diagram set up Apparatus to investigate refraction Place the glass block on a sheet of paper, and carefully draw around the rectangular perspex block using a pencil Switch on the ray box and direct a beam of light at the side face of the block A point on the ray close to the ray box The point where the ray enters the block The point where the ray exits the block A point on the exit light ray which is a distance of about 5 cm away from the block Draw a dashed line normal (at right angles) to the outline of the block where the points are Remove the block and join the points marked with three straight lines Replace the block within its outline and repeat the above process for a ray striking the block at a different angle Repeat the procedure for each shape of perspex block (prism and semi-circular) Analysis of results Consider the light paths through the different-shaped blocks Refraction experiment results with different media Refraction of light through different shapes of perspex blocks The final diagram for each shape will include multiple light ray paths for the different angles of incidences ( i ) at which the light strikes the blocks Label these paths clearly with (1) (2) (3) or A , B , C to make these clearer  Use the laws of refraction to analyse these results Evaluating the experiment Systematic errors. Use a set square to draw perpendicular lines Random errors Use a sharpened pencil and mark in the middle of the beam Use a protractor with a higher resolution Safety considerations Run burns under cold running water for at least five minute Avoid looking directly at the light Stand behind the ray box during the experiment Keep all liquids away from the electrical equipment and paper In your examination, you might be asked to write a method explaining how you might investigate the refraction of light through different shaped blocks As part of this method you should describe: What equipment you need How you will use the equipment How you will trace the rays of light before, while and after they pass through the block You've read 0 of your 10 free revision notes Unlock more, it's free, join the 100,000 + students that ❤️ save my exams. the (exam) results speak for themselves: Did this page help you? Electromagnetic Spectrum Simple Phenomena of Magnetism Electrical Quantities Electric Circuits & Electrical Safety Electromagnetic Effects The Nuclear Model of the Atom Radioactivity Earth & The Solar System Author: Katie M Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential. 300 IMAGES Refractive Index of Prism Experimental set-up for the measurement of refractive index by an Measuring refractive index To Determine The Refractive Index Of Liquid Using A Convex Lens And How do you Measure the Refractive Index? Schematic diagram of experimental setup for measuring refractive index VIDEO Refractive index experiment #experiment #shorts Physics experiment #lens #reflective #index Refraction of light #by #mithlesh_sir Spectrometer Happy Independence Day Refractive index #light #experiment #science #practical #class10 #class10 #schoolcurriculum #exams Experiment : to determine the refractive index of water by the help of convex lens and plane mirror COMMENTS PDF Experiment #17: Refraction Learn how to measure the angles of incidence and refraction of light beams at a boundary and calculate the index of refraction of different media. Use an online applet to perform the experiment and find the refractive indices of Lucite and mystery media. Make That Invisible! Refractive Index Matching This activity also requires some non-expendable lab supplies and equipment that are all reusable if properly stored after the activity; see the Materials List for details. ... refractive index matching is a significant tool enabling researchers to better observe what happens in experiments. Refractive index matching is tested by determining the ... Refraction Support. Many lab activities can be conducted with our Wireless, PASPORT, or even ScienceWorkshop sensors and equipment. For assistance with substituting compatible instruments, contact PASCO Technical Support. We're here to help. Use Snell's Law of refraction to experimentally determine the index of refraction of a D-shaped acrylic lens. Reflection and Refraction Snell's Law is explored and the index of refraction for a piece of acrylic material is found. PASCO Advantage: Students trace the rays on the provided templates and make angle measurements directly from their drawing. This reinforces the connection between the real rays they can see in the lab and the type of ray diagrams seen in the classroom. Determining Refractive Index Method. Apparatus to investigate refraction. Place the glass block on a sheet of paper, and carefully draw around the block using a pencil. Switch on the ray box and direct a beam of light at the side face of the block. Mark on the paper: A point on the ray close to the ray box. The point where the ray enters the block. PDF Measuring the Refractive Index This project compares three methods of measuring the refractive index of a medium using a concave mirror, a travelling microscope and Wollaston's method. The ... PDF Refractive index measurement principle Learn how the speed of light, Huygens' principle and critical angle are used to measure the refractive index of liquids with optical instruments. The web page explains the theory, geometry and practice of refractive index measurement with diagrams and examples. 15. Measurement of the refractive index of a material Risk. Control measure. Darkened laboratory. Physical injury if tripping on an object. Darkened or shaded laboratory - beware of tripping hazards as you will be working in reduced lighting. Ensure there is nothing on the floor which could be a hazard and make sure you only have the necessary equipment and apparatus on your work place. Measuring the Refractive Index of Liquid at a Defined Wavelength The refractive index is measured with a refractometer, which actually operates by measuring the limiting angle of refraction [Фl]. This angle indicates the point at which a light beam incident on a translucent surface of index [n] is no longer able to cross the surface, and instead is reflected, leading to a mirror effect in accordance with ... Measuring Refractive Index Method. Apparatus to investigate refraction. Place the perspex block on a sheet of paper, and draw around it using a pencil. Switch on the ray box and direct a beam of light at the side face of the block. Mark on the paper with a small 'x': A point on the ray close to the ray box. The point where the ray enters the block. Core Practical: Investigating Snell's law A diagram showing how to measure the angles of incidence and refraction. Snell's Law relates the angles of incidence and refraction. This is covered in the Snell's law revision note. Plot a graph of sin i on the y-axis against sin r on the x-axis. The refractive index is equal to the gradient of the graph. Index of Refraction: Glass Purpose: To use ray sightings to calculate the index of refraction of glass. Place the yellow paper on the cardboard. Place the glass plate in the center of the yellow paper and trace its outline in pencil. Place the straight pins into the paper along a slanted line between 2 to 5 cm from the top of the glass. Sight the base of the pins through ... Development of sound reflection and refraction experiment equipment The size of the experimental device is (500 × 50 × 200 mm) so students can directly experiment with it. The experimental apparatus is divided into three parts: (a) incident sound control, (b) reflected sound measurement, and (c) refraction sound measurement, as shown in figure 2. Zoom In. Zoom Out. Reset image size. Determination of the refractive index of a glass block To determine the refractive index of a glass block using the no-parallax method. low energy (very long wavelength) radio waves to high energy (short wavelength) Xrays/Gamma rays. When light rays strike the boundary between two media, the rays can undergo. several physical processes e.g. reflection, refraction, etc. PDF Physics 197 Lab 6: Reflection and Refraction 8. Using Snell's Law and your data, calculate the index of refraction for the Acrylic rhombus, assuming the index of refraction of air is one. Record the result for each of the three data sets in the table. 9. Average the three values of the index of refraction and compare to the accepted value (n = 1.493) using a percent difference. Refractive Index Learn what refractive index is and how to calculate it in this animated lecture by Najam Academy. Refractive index measures the optical density of a medium and depends on the speed of light in a ... PDF Experiment 6 Refraction of Light The speed of light in air is nearly identical to its speed in a vacuum; thus the index of refraction of air can be taken to be 1.00. The lower the speed of light in the material, the larger the index of refraction. n 1sinθ1 = n 2 sinθ2 (eq. 2) There is an inverse relation between index of refraction and angle. Measuring Refractive Index Method. Apparatus to investigate refraction. Place the perspex block on a sheet of paper, and draw around it using a pencil. Switch on the ray box and direct a beam of light at the side face of the block. Mark on the paper with a small 'x': A point on the ray close to the ray box. The point where the ray enters the block. (PDF) Refractive index of a transparent liquid measured ... Various experiments have been developed to confirm reflection and refraction. A method to measure the refractive index of solids and liquids with a simple instrument without the use of special ... Core Practical: Investigating Refraction Equipment: Purpose: Ray Box: To provide a narrow beam of light that can be easily refracted: Protractor: To measure the angles of incidence and refraction: Sheet of Paper: ... Refraction experiment set up. Apparatus to investigate refraction. Place the glass block on a sheet of paper, and carefully draw around the rectangular perspex block ... Required Practical: Investigating Reflection & Refraction Method. Apparatus to investigate reflection. Set up the apparatus as shown in the diagram. In the middle of the paper use a ruler to mark a straight line of about 10 cm long. Use a protractor to draw a 90° line that bisects (cuts in half) the 10 cm line. Place the mirror on the first line as shown in the diagram above. Refraction of Light Refraction occurs when light passes a boundary between two different transparent materials . At the boundary, the rays of light change direction; This change in direction depends on the difference in density between the two media:. From less dense to more dense (e.g air to glass), light bends towards the normal. From more dense to less dense (e.g. glass to air), light bends away from the normal essay homework paper phd project resume review speech study thesis