# How Many Photons are Emitted Per Second by a Helium Neon Laser?

What is the formula to calculate the number of photons emitted per second by a laser? How many photons are emitted per second by a 9.20 mW helium neon laser with a wavelength of 633 nm?

The number of photons emitted per second by a laser can be calculated using the formula: Number of photons per second = Power of laser / Energy per photon In this case, we have the power of the laser as 9.20 mW (milliwatts) and the wavelength as 633 nm (nanometers). To calculate the energy per photon, we can use the equation: Energy per photon = Planck's constant (h) * speed of light (c) / wavelength Planck's constant is approximately 6.626 × 10^-34 Joule-seconds and the speed of light is approximately 3.00 × 10^8 meters per second. Converting the wavelength from nanometers to meters, we have: Wavelength = 633 nm * (1 meter / 10^9 nanometers) = 6.33 × 10^-7 meters Substituting the values into the equation, we get: Energy per photon = (6.626 × 10^-34 J·s) * (3.00 × 10^8 m/s) / (6.33 × 10^-7 m) Calculating this, we find the energy per photon to be approximately 3.12 × 10^-19 Joules. Now, we can calculate the number of photons per second: Number of photons per second = (9.20 × 10^-3 W) / (3.12 × 10^-19 J) Dividing these values, we find the number of photons emitted per second to be approximately 2.95 × 10^15 photons. Therefore, approximately 2.95 × 10^15 photons are emitted per second by the 9.20 mW helium neon laser with a wavelength of 633 nm.

## Calculation of Number of Photons Emitted

**Formula:**Number of photons per second = Power of laser / Energy per photon