Question

For a given frequency, what determines the intensity of light in the photon picture?

Options

• The speed of wave propagation

• The thickness of the lens at its centre

• The time taken along the ray going through the centre alone

• The number of photons crossing a unit area per unit time

Answer 1

At a given frequency, photon-picture intensity depends on how many photons cross a unit area per unit time. A greater number gives greater intensity.