A beam of light $P$ has twice the wavelength but the same intensity as beam $Q$. The number of photons that hit a given area in a given time when it is illuminated by beam $P$ is (A) twice, (B) the same, or (C) one-half of the number that hit when the area is illuminated by beam $Q$ ?
A) Twice}
B) The Same
C) One-half of the number that hit

Question

Quizplus · Accepted Answer

The number of photons is inversely proportional to the wavelength. Since the wavelength of beam P is twice that of beam Q, the number of photons in beam P is one-half that of beam Q.

A Beam of Light PPP Has Twice the Wavelength but the Same Intensity as Beam

A Beam of Light $P$ Has Twice the Wavelength but the Same Intensity as Beam