Question

Two lasers shine red light at 650 nm. One laser is twice as bright as the other. Explain this difference using photons and photon energy.

a) The bright laser has more photons.

b) The bright laser has higher-energy photons.

c) The bright laser has a lower frequency.

d) The bright laser has a longer wavelength.

Answer 1

The brighter laser emits twice as many photons as the dimmer one, but the energy per photon remains the same since both lasers emit red light of the same wavelength.

Step-by-step explanation:

The difference in brightness between the two lasers that emit red light at 650 nm can be explained by the number of photons they emit. Since both lasers emit light of the same wavelength (and hence, the same frequency), the energy of individual photons from both lasers is the same. The brightness of a laser correlates with the intensity of the light it emits, which in turn is directly proportional to the number of photons emitted per second. Therefore, if one laser is twice as bright as the other, it is because the brighter laser emits twice the number of photons compared to the other laser, but both lasers emit photons with equivalent amounts of energy per photon.