Calculate the Number of Photons Emitted by a He-Ne Laser

How many photons does a 2.1 mW He-Ne laser emit in one second?

a. 3.32 x 10^16 photons

Answer:

The He-Ne laser emits approximately 3.32 x 10^16 photons in one second.

The He-Ne laser emits photons as a result of energy transitions within its atoms. These photons have a specific wavelength and energy associated with them. In this case, the laser beam has a power of 2.1 mW and a wavelength of 633 nm. By calculating the energy of one photon and using the power of the laser, we can determine the number of photons emitted per second.

To start, we converted the laser power from milliwatts to watts, which is 2.1 x 10^-3 W. Then, we calculated the energy of one photon using Planck's constant, the speed of light, and the given wavelength. The energy of one photon was found to be 9.89 x 10^-19 J.

Using the formula Number of photons = Power / Energy of one photon, we determined that the He-Ne laser emits approximately 3.32 x 10^16 photons in one second. This calculation provides insight into the quantum nature of light and the behavior of lasers in emitting photons.