# How many photons are produced in a laser pulse of

How many photons are produced in a laser pulse of 0.528 J at 679 nm?

## General guidance

Concepts and reason

The concept used in this question is Plank’s equation. This equation is used to find the energy of the photon. Initially, the energy of photons released by one photon at a given wavelength is calculated by using the expression of plank’s equation. Lastly, the number of photons released by laser pulse at energy is determined by using the concept of plank’s equation.

Fundamentals

Plank’s equation Photons are described as the energy packets of light that travel with the speed of light. It has no mass and is electrically neutral. The energy of a photon is given by Plank’s equation which is expressed as follows. …… (1) Here, is the energy of photons, is the number of photons, is the Plank’s constant , is the speed of light , and is the wavelength of the photon.

## Step-by-step

### Step 1 of 2

The units of wavelength from to can be converted as given below. So, the conversion of a unit of wavelength from to is done as follows. Substitute as wavelength and in the equation to calculate the energy released by one photon. The unit of wavelength is changed from nanometer to meter using the conversion factor as mentioned above. Then, substitute as wavelength in the expression of the Plank’s equation, the energy released by one photon is calculated.

### Step 2 of 2

The number of photons released by energy is calculated as shown below. The number of photons released by a laser pulse of energy is at  .

The energy released by one photon is energy. So, the number of photons released by a laser pulse of energy is calculated by the expression of Plank’s equation.

The number of photons released by a laser pulse of energy is at  .