1: Reflection
When waves hit a surface they can be reflected.
Norm
Using the simulation answer the questions below.
phet.colorado.edu/sims/html/bending-light/latest/bending-light_en.html
Angle
θ
Angle of
1.a. What is the relationship between the angles of incidence and reflection?
angle of incidence is the original light angle and the reflection angle is the angle
after the light is reflected
1.b What do you notice about the strength of the reflected beam?
The light becomes weaker after being reflected
1.c Does changing the index of refraction (n) affect the angle of the reflected ray?
yes
2: Refraction
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
7.5
.173
.130
.133
20
14.8
.342
.255
1.34
30
22.1
.5
.374
1.33
40
28.8
.642
.481
1.33
50
35
.766
.573
1.33
60
40.5
.866
.649
1.33
70
45
0.940
0.707
1.33
80
47.5
.984
.737
1.33
2.a. What is the relationship between the angles of incidence and refraction?
angle of incidence is the original light angle and the reflection angle is the angle
after the light is reflecte
2.b What do you notice about how the strength of the refracted beam changes with θi?
Beam becomes weaker
3: Refraction (Changing Materials)
Now try changing the materials at the bottom only.
3.a What effect does increasing the index of refraction of the
bottom material have?
Changes refraction more
3.b Does the ray bend toward or away from the normal?
Is that always true when air is the top material?
away , yes
Now try changing both the materials.
3.c What patterns do you notice?
Matching materials makes beam refract less than being complete oppoisite
3.d How can you make the ray bend away from the normal?
Air top, glass bottom
Now set up the materials as water on
top and air on the bottom.
Move the laser back and forth
3.e Somewhere between 30o and 60o the behaviour changes.
What is the exact angle?
48.5
3.f What happens at this angle?
Beam refracts from 48.5 - 0 and doesnt refracts 90 - 48.6