Question

Consider a laser pointer that emits red light with wavelength 650 nm. This light is used for a photoelectric effect experiment where the anode in the evacuated glass tube is made up of a material that has work function equal to 1 eV. 1. What is the energy of an individual photon that comes out of the laser pointer?

Answer 1

The energy of an individual photon that comes out of the laser pointer is 1.91 eV

Step-by-step explanation:

The energy of a photon can be obtained using the expression below

E = hc/λ

where E is the energy;

h is the Planck's constant = 6.626 x 10-34 Js;

c is the speed of light = 3.00 x
`10^(8)` m/s (speed of light);

λ is the wavelength = 650 nm =650 x
`10^(-9)` m.

E = (6.626 x 10-34 Js) x (3.00 x
`10^(8)` m/s) /650 x
`10^(-9)` m

E = 3.058 x
`10^(-19)` J

1 joule = 6.242 x
`10^(18)` eV

3.058 x
`10^(-19)` J = 3.058 x
`10^(-19)` J x 6.242 x
`10^(18)` eV = 1.91 eV

Therefore the energy of an individual photon that comes out of the laser pointer is 1.91 eV