Question

Calculate the energy of the red light emmitted by a neon atom with wavelength of 680 nm.

a) 1 x 10

b) J

Answer 1

The red light will consist of photons and they only carry the energy of light.

According to Planck's-Einstein's relation,

E=h.

where E= energy of photon,

h= Planck's constant = 6.626*10^-34 J.s

= frequency of the light

Also, = c/

where c= speed of light = 3*10⁸ m/s

& = wavelength of light = 680 nm   (given)

1 nm =10^-9 m

So, = 680*10^-9 m

putting this in above expression,

E=(h.c)/ = (6.626*10^-34)*(3*10⁸)/(680*10^-9) = 2.9*10^-19 J

Thus energy of light is 2.9*10^-19 J