Physics Waves and Optics 2

Question 1

A wave travels from a medium where its speed is 300 m/s into a medium where its speed is 200 m/s. How does the wavelength change?

Accepted Answer

It decreases by one-third

Answer

Since frequency is constant at a boundary, wavelength is proportional to wave speed, so it decreases by the same ratio (200/300 = 2/3).

Question 2

Which phenomenon causes a swimming pool to appear shallower than it actually is?

Accepted Answer

Refraction

Answer

Refraction bends light as it exits the water, making objects appear closer to the surface than they are.

Question 3

Two speakers emit sound waves of the same frequency in phase. At a point where the path length difference is 1.5 wavelengths, what occurs?

Accepted Answer

Destructive interference

Answer

A path difference of 1.5λ (a half-integer multiple) means the waves arrive out of phase, causing destructive interference.

Question 4

The speed of light in glass is 2.0 × 10⁸ m/s. What is the index of refraction of the glass?

Accepted Answer

1.5

Answer

n = c/v = (3.0 × 10⁸)/(2.0 × 10⁸) = 1.5.

Question 5

A longitudinal wave is characterized by particles oscillating in what direction relative to wave propagation?

Accepted Answer

Parallel

Answer

In longitudinal waves, particle displacement is parallel (along) the direction of wave travel, forming compressions and rarefactions.

Physics Practice Test