Two sources emit beams of microwaves.The microwaves from source A have a frequency of 10 GHz,and the ones from source B have a frequency of 20 GHz.This is all we know about the two beams.Which of the following statements about these beams are correct? (There could be more than one correct choice. )
A)Beam B carries twice as many photons per second as beam A.
B)A photon in beam B has twice the energy of a photon in beam A.
C)The intensity of beam B is twice as great as the intensity of beam A.
D)A photon in beam B has the same energy as a photon in beam A.
E)None of the above statements are true.

Question

Quizplus · Accepted Answer

The energy of a photon is given by E = hf, where h is Planck's constant and f is the frequency of the photon. 
Therefore, since the frequency of the microwaves from source B is twice that of the microwaves from source A, each photon in beam B has twice the energy of a photon in beam A. All the other statements are not necessarily true, as they depend on other factors such as the number of photons and the direction of the beams.

Two Sources Emit Beams of Microwaves