Physics Waves and Optics 3

Question 1

What is the critical angle for total internal reflection if the index of refraction of a medium is 1.5 (relative to air)?

Accepted Answer

41.8°

Answer

sin(θ_c) = 1/n = 1/1.5 = 0.667, so θ_c = arcsin(0.667) ≈ 41.8°.

Question 2

In a double-slit experiment, what happens to the fringe spacing if the distance between the slits is doubled?

Accepted Answer

Fringe spacing is halved

Answer

Fringe spacing Δy = λL/d; doubling d halves the spacing.

Question 3

A wave on a string has a frequency of 50 Hz and a wavelength of 0.4 m. What is its speed?

Accepted Answer

20 m/s

Answer

v = fλ = 50 Hz × 0.4 m = 20 m/s.

Question 4

Which type of electromagnetic wave has the longest wavelength?

Accepted Answer

Radio waves

Answer

Radio waves occupy the lowest-frequency, longest-wavelength end of the electromagnetic spectrum.

Question 5

A diverging lens always produces images that are:

Accepted Answer

Virtual and upright

Answer

A diverging (concave) lens always produces virtual, upright, and diminished images on the same side as the object.

Physics Practice Test