A helium-neon laser emits light of wavelength 632.8 nm and has a power output of 3 mW. How many photons are emitted per second by this laser? A) 9.55 × 10¹⁴ B) 9.55 × 10¹⁵ C) 8.24 × 10¹⁵ D) 6.53 × 10¹⁵ E) 4.78 × 10¹⁵

Question

Quizplus · Accepted Answer

The energy of one photon can be calculated using the equation:

E = hc/λ

where h is Planck's constant (6.626 × 10^-34 J s), c is the speed of light (3.00 × 10^8 m/s), and λ is the wavelength of the light.

Plugging in the values given in the problem, we get:

E = (6.626 × 10^-34 J s)(3.00 × 10^8 m/s)/(632.8 × 10^-9 m)
E = 3.14 × 10^-19 J

To find the number of photons emitted per second, we need to know the total energy emitted per second (i.e. the power output), and divide by the energy of one photon:

number of photons emitted per second = power output/energy of one photon
number of photons emitted per second = (3 × 10^-3 W)/(3.14 × 10^-19 J)
number of photons emitted per second = 9.55 × 10^15

Therefore, the answer is B, 9.55 × 10^15.

A Helium-Neon Laser Emits Light of Wavelength 632