Question

what is the wavelength of a photon that has two times less energy than that of a photon whose wavelength is 200 nm?

Answer 1

We know that Energy, E = hc / λ

Where

h = plank's constant = 6.625x 10^-34 Js

c = speed of light = 3x 10⁸ m/s

λ = wave length

As E is inversly proportional to λ

E / E' = λ ' / λ

Where

E = energy of photon whose wavelength is 200 nm = 2xE'

E' = energy of required photon

λ = wave length of initial photon = 200 nm

λ' = wavelength of required photon = ?

Plug the values we get

λ ' = (Ex λ ) / E'

    = (2xE' x 200) / E'

    = 400 nm

So the required wavelength = 400 nm