Question

Neon discharge tubes emit a light with a wavelength of 600. Nm that appears deep orange to the human eye. How many photons of this electromagnetic radiation amount to 250. J of energy?

Answer 1

`7.53\cdot 10^(20)`

Step-by-step explanation:

The energy of a photon of wavelength
`\lambda` is given by

`E=(hc)/(\lambda)`

where

`h = 6.63\cdot 10^(-34) Js` is the Planck constant

`c=3\cdot 10^8 m/s` is the speed of light

In this problem, the wavelength of the photon is

`\lambda=600 nm=600\cdot 10^(-9) m`

So the energy of one photon with this wavelength is

`E_1=((6.63\cdot 10^(-34) Js)(3\cdot 10^8 m/s))/(600\cdot 10^(-9) m)=3.32\cdot 10^(-19) J`

In order to have a total energy of E = 250 J in this radiation, we have to divide this value by the energy of a single photon, so we find the number of photons that we need:

`n=(E)/(E_1)=(250 J)/(3.32\cdot 10^(-19) J)=7.53\cdot 10^(20)`