Question: Which equation describes the photoelectric effect?

Options:

1. E = mc^2
2. E = hf - φ
3. E = 1/2 mv^2
4. E = kx

Correct Answer: E = hf - φ

Solution:

The equation E = hf - φ describes the photoelectric effect, where E is the kinetic energy of the emitted electron, hf is the energy of the incident photon, and φ is the work function.