A helium-neon laser emits light at 632.8 nm. If the laser emits $1.82 \times 10^{17}$ photons/second, what is its power output in mW? (c = 3.00 × 10⁸ m/s, h = 6.626 × 10^-34 J ∙ s)

Question

Quizplus · Accepted Answer

The energy of one photon can be calculated using the formula:
$$E = \frac{hc}{\lambda}$$
where h is Planck's constant, c is the speed of light, and $\lambda$ is the wavelength of the photon. Substituting the given values, we get:
$$E = \frac{(6.626 	imes 10^{-34} 	ext{ J s})(3.00 	imes 10^8 	ext{ m/s})}{632.8 	imes 10^{-9} 	ext{ m}} \approx 3.14 	imes 10^{-19} 	ext{ J/photon}$$
The power output can be calculated as the product of the energy of one photon and the number of photons emitted per second:
$$P = (1.82 	imes 10^{17} 	ext{ photons/s})(3.14 	imes 10^{-19} 	ext{ J/photon}) \approx 5.72 	ext{ mW}$$
Therefore, the best choice is A) 57.2 mW (the answer is given in milliwatts, not watts, as in the calculation).

A Helium-Neon Laser Emits Light at 632 1.82×10171.82 \times 10^{17}1.82×1017 Photons/second, What Is Its Power Output in MW? (C =

A Helium-Neon Laser Emits Light at 632 $1.82 \times 10^{17}$ Photons/second, What Is Its Power Output in MW? (C =