A Helium-Neon Laser Emits Red Light Having a Wavelength of 6.4

Multiple Choice

A helium-neon laser emits red light having a wavelength of 6.4 × 10−⁷ m and a power of 0.5 mW. How many photons are emitted each second?

A) 6.4 × 10³⁸
B) 1.6 × 10²¹
C) 3.2 × 10²⁵
D) 2.6 × 10¹⁸
E) 1.6 × 10¹⁵