PHYS-122- PhET-Expt-10: Bending Light
Name: Class/Section: Date:
Lab Report:
Use this Lab Handout as guidelines to do the experiments, to collect the data, record the data and answer any questions there in this Handout. Then at the end of the Handout, as the additional part of the Lab Report, please add the following items:
Purpose:
Equipment:
Procedure:
Data and Data Analysis:
Results:
Conclusion:
Each item of the Lab Report needs to be at least a paragraph long with Pictures, data-tables or screenshots when needed, even if those are repeats from the Handout items.
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Take screenshots at different stages of the experiment and use those screenshots for the Handout part and repeat in the Lab Report part, where applicable.
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Equipment in PhET simulation need to be described in detail and not only just say I used PhET simulation.
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In procedure, please describe in detail about what are the steps that you did to do the experiment and to collect the data.
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So, the Lab Report will have the Handout part at the beginning and then also the additional parts at the end that will include the above 6 items. Then save this whole WORD file as one single WORD file (or any other format) and submit this full Lab Report in Blackboard on the Assignment page of the Blackboard.
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Experiment:
Please go to the following link to open the PhET-Simulation for this Lab Experiment and play with it for a few minutes first.
Link: https://phet.colorado.edu/en/simulation/bending-light
Link: https://phet.colorado.edu/en/simulation/bending-light
1: Reflection
When waves hit a surface they can be reflected.
Angle of reflection
θr
Angle of incidence
θi
Normal line
Angle of reflection
θr
Angle of incidence
θi
Normal line
Using the simulation answer the questions below.
phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html
1.a. What is the relationship between the angles of incidence and reflection
Angle of Incidence = Angle of reflection
θi = θr
1.b What do you notice about the strength of the reflected beam?
1.c Does changing the index of refraction (n) affect the angle of the reflected ray?
2 Refraction
Angle of refraction
Angle of incidence
θi
θr
Angle of refraction
Angle of incidence
θi
θr
Often part of the wave is transmitted.
If the wave changes speed it will bend.
This is called refraction.
Reset the simulation
Set up the simulation with a protractor carefully placed centered on the normal.
phet.colorado.edu/sims/html/bending-light/
latest/bending-light_en.html
Complete the table below
Incident angle ,θi
Refracted angle ,θr
sin(θi)
sin(θr)
sin(θi) /sin(θr)
10
20
30
40
50
60
70
45
0.940
0.707
1.____
80
2.a. What is the relationship between the angles of incidence and refraction
This relationship is defined by Snell’s Law and expressed as follows:
n1 sin(θi) = n2 sin(θr)
where n1 is the index of refraction of Media 1 and n2 is the Index of Refraction of Media 2
2.b What do you notice about how the strength (intensity) of the refracted beam changes with θi ?
Now try changing the materials at the bottom only .
2.c What effect does increasing the index of refraction of the bottom material have?
2.d Does the ray bend toward or away from the normal?
Is that always true when air is the top material?
Now try changing both the materials .
2.e What patterns do you notice?
2.f How can you make the ray bend away from the normal?
Now set up the materials as water on top and air on the bottom.
Move the laser back and forth
2.h Somewhere between 30o and 60o the behaviour changes.
What is the exact angle?
2.i What happens at this angle
3 Critical angle
When going from a more to a less dense material.
The light ray should be r________ away from the n_______
At the critical angle the behaviour suddenly changes and the totality of all light is reflected back internally into the water.
This is called _________ ___________ ________ion
Complete the table below (use air as the bottom material)
TOP Material
Refractive index (n)
critical angle ,θc /o
sin ,θc
1 / sin θc
Water
1.33
48
0.743
1.35
Glass
Mystery A
4 The PHYSICS 🙂
Go to the More Tools page of the simulation
phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html
Use the Wave setting at 650nm.
Keep the top material as Air
4.a. Look at the wavefronts as they enter the glass.
What happens to the speed, wavelength and frequency of the wave? (by eye)
Speed:
Wavelength:
Frequency:
Use the Time tool to show the wave of the refracted and reflected rays
4.b. Are the frequencies of the refracted and reflected waves the same or different?
Use the Speed tool to find the velocity of incident, refracted and reflected rays
Bottom material
Wave Speed
Type
n
1/n
Incident
Reflected
Refracted
Air
Water
1.33
1.00
0.67
Glass
5 The Dark side of the PhET
On the Prisms page of the simulation
phet.colorado.edu/sims/html/bending-light/
latest/bending-light_en.html
Select the white on black colour scheme
Set up the triangular block as shown.
Ensure the ray is pointed near the tip
5.a. Describe what you see.
Go to the More Tools page of the simulation
Use the spectrum to
investigate how colour chages with wavelength
Complete the table
Wavelength nm
400
450
525
580
600
650
700
Colour
Yellow
5.b. Describe the relationship between colour and wavelength.
5.c. Looking at the spectrum produced by the prism, which colour is bent more?
5.d. Use this to explain which colour slows down the most in a glass block
6 Rainbows (Extension)
On the Prisms page of the simulation
phet.colorado.edu/sims/html/bending-light/
latest/bending-light_en.html
Turn on reflections and use a circular prism
See if you can produce a spectrum.
In a rainstorm lots of small spherical droplets fall from the clouds
Can you explain….
8.a. What conditions are needed for a rainbow
8.b. Is there only one position you might see a rainbow?
Lab Report:
Each item of the Lab Report needs to be at least a paragraph long with Pictures, data-tables or screenshots when needed, even if those are repeats from the Handout items.
==
Take screenshots at different stages of the experiment and use those screenshots for the Handout part and repeat in the Lab Report part, where applicable.
==
Equipment in PhET simulation need to be described in detail and not only just say I used PhET simulation.
==
In procedure, please describe in detail about what are the steps that you did to do the experiment and to collect the data.
==
1) Purpose:
2) Equipment:
3) Procedure:
4) Data and Data Analysis:
5) Results:
6) Conclusion: