Question

How do you calculate the number of photons?

Answer 1

Hint: The term photon is related to the electromagnetic radiations. We can calculate the energy of a photon and use this total energy to calculate the number of photons. The number of photons will be the ratio of total energy to the energy of one photon, in general.

Complete step by step solution:
Let us learn about the electromagnetic waves and radiations;
An electromagnetic-waves carries energy with it while transportation and this depends upon the number of photons it can take along per second. The amount of energy per photon depends on the wavelength of waves and the frequency.
The energy of photons can be expressed as;
$$E=nh\nu =n{\displaystyle \frac{hc}{\lambda }}$$
where,
n = number of photons
h = planck's constant
$\nu$ = frequency
c = speed of light
$\lambda$ = wavelength
Now, as we have to calculate the number of photons using this equation, we will preferably rearrange the above equation as,
$${\displaystyle \frac{E}{h}}=n\nu$$
The term $n\nu$ has the unit of photons per second.

Note: Do note that we have two methods to calculate the number of photons as described but at the end we reach the same point of interest and the same results are obtained.