A light-emitting diode emits one microwatt of 640 nm photons. How many photons are emitted each second? A)2.5 × 10²⁰ B)9.7 × 10²⁰ C)2.0 × 10³¹ D)3.0 × 10²¹ E)3.2 × 10¹²

Question

Quizplus · Accepted Answer

The energy of one photon is given by E = hc/λ, where h is Planck's constant (6.626 × 10^-34 J·s), c is the speed of light (3 × 10^8 m/s), and λ is the wavelength (640 nm = 640 × 10^-9 m). Calculate the energy per photon and divide the total power (1 microwatt = 1 × 10^-6 W) by this energy to find the number of photons emitted per second.

A Light-Emitting Diode Emits One Microwatt of 640 Nm Photons