12.3 - Refraction

Get the Assessment: FA12.3.docx

Written Solutions: http://tuhsphysics.ttsd.k12.or.us/Tutorial/NewIBPS/PreQuiz/12.3/12.3.htm

1. You hear the sound of a hammer striking concrete 1.21 seconds sooner in the concrete than through the air. If the speed of sound through the air is 339 m/s, and the hammer is 724 m away, what is the speed of sound in the concrete?

(782 m/s)

Questions 2-5 are about the light from a 640 nm laser. (640 nm is its wavelength, 1 nm = 10^-9 m)

2. What is the speed of the laser light in Lucite? (n = 1.51) (1.99x10⁸m/s)

3. What is the wavelength and frequency of the light in Lucite? (n = 1.51)

(424 nm, 4.69x10¹⁴ Hz)

4. The laser goes from air into the Lucite. It makes the angle shown in the diagram below. Calculate the refracted angle in the Lucite, draw the refracted beam, and label the angle.

(32.4^o)

5. What is the critical angle between air and Lucite? In which substance does it occur?

(41.5^o – in the Lucite)

The Practice Problems:

P12.3 – Refraction and Critical Angle Problems.

0. Sound travels at 1498 m/s in water, and 343 m/s in the air. An explosion occurs on the surface of the water 1250 m away. What time does it take the sound to reach you in the air? What time does it take the sound to reach you in the water? What amount of time separates the arrival of the sound in the water and in the air?

(Air: 3.644 s, Water: 0.834 s, Difference: 2.81 s)

1. A 632.8 nm laser has an incident angle of 45.0^o in air and strikes some oil with an index of refraction of 1.54.

a. What is the frequency of the laser? (4.74x10¹⁴ Hz)

b. What is the wavelength of the laser in the oil? (411 nm)

c. What is the refracted angle in the oil? (27.3^o)

d. What is the critical angle at the oil air interface? In which medium does the critical angle occur?

(40.5^o, in the oil – the slower medium)

2. Light has a wavelength of 356 nm in glass. It passes from the glass into water with an index of refraction of 1.33. The incident angle in the glass is 29.0^o and the refracted angle in the water is 37.0^o.

a. What is the index of refraction of the glass? (1.65)

b. What is the wavelength of the light in the water? (442 nm)

c. What is the critical angle of the glass water interface? In which medium does it occur?

(53.7^o, in the glass – the slower medium)