Question

The wavelength of incident light is 4000 Å. Calculate the energy of the incident photon.

Answer 1

Given:

Wavelength (λ) = 4000 Å 

= 4000 × 10⁻¹⁰ m

= 4 × 10⁻⁷ m

Planck’s constant (h) = 6.626 ×10⁻³⁴ J/s

Speed of light (c) = 3.0 ×10⁸ m/s

Formula:

E = hv

Since `v = c/lambda`

`E = (hc)/lambda`

`E = ((6.626 xx 10^-34) xx (3.0 xx 10^8))/(4.0 xx 10^-7)`

`E = (1.9878 xx 10^-25)/(4.0 xx 10^-7)`

E = 4.97 × 10⁻¹⁹ J