A laser emits a single, 3.0-ms pulse of light that has a frequency of 2.83 × 10¹¹ Hz and a total power of 65 000 W. How many photons are in the pulse? A)6.0 × 10²³ B)1.2 × 10²⁴ C)2.4 × 10²⁵ D)3.6 × 10²⁵ E)4.8 × 10²⁶

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Quizplus · Accepted Answer

The energy of a single photon is given by E = hf, where h is Planck's constant (6.626 × 10^-34 J·s) and f is the frequency. The total energy of the pulse is power × time = 65,000 W × 3.0 × 10^-3 s. Dividing the total energy by the energy per photon gives the number of photons.

A Laser Emits a Single, 3