AP Physics Physics: Thermodynamics & Modern Physics 4

Question 1

Blackbody radiation peaks at a shorter wavelength when the temperature of the object:

Accepted Answer

Increases

Answer

Wien's displacement law states λ_max = b/T; higher temperature shifts the peak to shorter wavelengths.

Question 2

An ideal gas undergoes an isothermal expansion. Which of the following is true?

Accepted Answer

Heat is absorbed by the gas

Answer

In isothermal expansion, ΔU = 0 for an ideal gas, so Q = W > 0; the gas must absorb heat to do work.

Question 3

Which of the following particles carries a charge of +1e and has a mass of approximately 1 atomic mass unit?

Accepted Answer

Proton

Answer

A proton carries a charge of +1e and has a mass of approximately 1.67 × 10⁻²⁷ kg, or ~1 amu.

Question 4

The photoelectric effect provided evidence that light:

Accepted Answer

Consists of discrete packets of energy called photons

Answer

The photoelectric effect demonstrated that light energy is quantized into photons, each with energy E = hf.

Question 5

For an isochoric (constant volume) process, the work done by the gas is:

Accepted Answer

Zero

Answer

At constant volume, ΔV = 0, so W = PΔV = 0; all heat goes into changing internal energy.

AP Practice Test