OAT Physics: Optics and Waves 3

Question 1

A concave mirror has a radius of curvature of 30 cm. An object is placed 45 cm in front of it. The image distance is:

Accepted Answer

22.5 cm in front

Answer

Focal length = R/2 = 15 cm; 1/f = 1/do + 1/di → 1/15 = 1/45 + 1/di → di = 22.5 cm in front (real image).

Question 2

In Young's double-slit experiment, if the slit separation is doubled while keeping all else constant, the fringe spacing:

Accepted Answer

Is halved

Answer

Fringe spacing Δy = λL/d, so doubling slit separation d halves the fringe spacing.

Question 3

The Doppler effect for sound predicts that as a source moves toward a stationary observer, the observed frequency:

Accepted Answer

Increases

Answer

As the source approaches, wavefronts are compressed, increasing the observed frequency (blue shift for sound).

Question 4

Which color of visible light has the greatest energy per photon?

Accepted Answer

Violet

Answer

Photon energy E = hf = hc/λ; violet light has the shortest wavelength (~400 nm) and thus the highest frequency and energy.

Question 5

A light ray travels from water (n = 1.33) into glass (n = 1.52). The ray bends:

Accepted Answer

Toward the normal

Answer

When light enters a denser medium (higher n), it bends toward the normal per Snell's law.

OAT - Optometry Admission Test Practice Test