Snell’s Law Problems
𝑛1 𝑠𝑖𝑛(𝜃𝑖 ) = 𝑛2 𝑠𝑖𝑛(𝜃𝑟 )
Directions: Solve all problems in your notebook. Draw a diagram for each problem.
Material
Vacuum
Air
Water
Ethyl Alcohol
Acryllic
Amber
Mercury
Sapphire
Cubic Zirconium
Diamond
Silicon
Index of Refraction
1
1.00
1.33
1.36
1.50
1.55
1.62
1.77
2.16
2.42
3.96
1) Alison sees a coin at the bottom of her swimming pool at an angle of 40° to
the normal and she dives to retrieve it. However, Alison doesn’t like to open
her eyes in the water so she must rely on her initial observation of the coin
made in the air. At what angle does the light from the coin travel as it moves
towards the surface?
2) Robert makes his girlfriend a romantic candlelight dinner and tops it off with
a dessert of gelatin filled with blueberries. If a blueberry that appears at an
angle of 44° to the normal in air is really located at 30° to the normal in the
gelatin then what is the index of refraction in the gelatin?
3) Light moves out of air into an unknown material. It enters at an angle of
incidence of 40° and has an angle of refraction of 25.37°. What material did
it enter?
4) Light moves out a flashlight beneath the water into air. It enters at an angle
of 45° to the vertical. With what angle with the vertical does it make when it
exits the water?
5) A light beam coming from an underwater spotlight exits the water into air at
an angle of 66° to the vertical. At what angle of with the vertical does it
approach the air from below the surface?
6) Light is shined from air into an ancient amber block containing fossilized
insects at an angle of 20° to the surface of the block. When the light enters the
block what is its angle of refraction?
7) Heather is snorkeling in Oahu’s Hanauma Bay when she looks up through the
water at a palm tree on the shore. If heather sees the palm tree at an angle of
48° to the vertical, at what angle is the palm tree really located with respect
to the vertical?
8) Spenser, a cat, enjoys watching the family goldfish from the top of the tank. If
the goldfish, swimming in the water, appears to be at an angle of 28° to the
vertical as seen by Spenser, at what true angle is the goldfish from the normal
in the water?
9) Kibala’s wife (much to Mr. Kibala’s dismay) decided to see if her ring was
really made of diamond. She shines light at an angle of incidence of 60
degrees into her ring and measures an angle of refraction to be 23.64
degrees. What is her ring made of?
10)The index of refraction of ethyl alcohol is 1.36 while the index of refraction of
water is 1.33.
a. Does light travel faster is alcohol or water?
b. What is the speed of light in each?
11) The speed of light in Sweet Tea is 2.08 x 108 m/s and the speed of light in
unsweetened iced tea is 2.22x108 m/s.
a. Calculate the index of refraction of sweet tea and unsweetened iced
tea.
b. Which tea is more optically dense?
12)A light ray travelling through air has an angle of incidence of 39.7o. The light
then enters into another medium at an angle of refraction of 28o.
a. On the diagram below draw how light travels through the air into the
unknown medium. (Use a protractor to help you do this question).
Normal line
air
unknown
medium
b. On the diagram above label which medium is more dense and which is
less dense.
c. Calculate the index of refraction for the unknown medium.
d. What is the unknown medium?
Answers Snells law:
1) 28.9°
2) 1.39
3) Acryllic
4) 70.12°
5) 43.38°
6) 37.32°
7) 81.26°
8) 20.67°
9) cubic zirconium
10) b. 2.21x108, 2.26x108
11) 1.348, 1.439
12) bottom is more dense, 1.36, ethyl alcohol.