Physics 142
Name
Refraction and Lenses Bonus Activity
Recitation section ______
For full credit due
by 2:30 pm, Friday, 9/29/00
12 points
Two points each.
1. A ray of light is incident upon an air-water surface.
Measure all three angles, i.e. incidence, reflection and refraction. What which direction is the
light coming? Explain your answer. What is the index of refraction of the water? How does your
result to compare to typical values for water?
2. A ray of light is incident upon an air-glass interface at an angle of incidence very close to the
critical angle. From which direction is the light coming? Explain your answer.
Measure the critical angle. Use it to compute the index of refraction of the glass.
3. Five parallel rays of light pass through this lens. Assume the picture is actual size.
What kind of lens is it? Determine the focal length of the lens. Explain your work. Explain the
weak rays that appear to be going to the left.
4. Five parallel rays of light(from the left) pass through this lens. Assume the picture is actual size.
What kind of lens is it? Determine the location of the focal point of the lens. How do you explain
the apparent focal point caused by the weakly reflected light rays? Compare the two different
local lengths. How do you explain their difference?
5. Five rays of light are incident upon a combined system of two lenses. Assume the picture is
actual size.
Determine the focal length for each of the two lenses and then the focal length of the
combination of the lenses. Determine a rule for computing the focal length of a combined lens
system. How do you explain the focal point of the weakly showing rays? How do you explain the
colors in the "white" light at the very right edge of the photograph?
6. Five parallel rays of light(from the left) are incident upon a system of two lenses which are
placed with their optical axes in coincidence. Assume the picture is actual size.
Determine the focal length for each of the two lenses and then the focal length of the
combination of the lenses. Determine a rule for computing the focal length of a combined lens
system. How do you explain the apparent weak focal point between the two lenses?