Question

What is the energy of a single photon of blue light with a wavelength of 488 nm (488 × 10-9 m)?

Answer 1

Answer : The energy of a photon is, $4.073\times 10^{-19}J$

Explanation :

Formula used :

$E=\frac{h\times c}{\lambda}$

where,

E = energy = ?

h = Planck's constant = $6.626\times 10^{-34}Js$

c = speed of light = $3\times 10^8m/s$

$\lambda$ = wavelength = $488\times 10^{-9}m$

Now put all the given values in the above formula, we get the energy.

$E=\frac{(6.626\times 10^{-34}Js)\times (3\times 10^8m/s)}{488\times 10^{-9}m}$

$E=4.073\times 10^{-19}J$

Therefore, the energy of a photon is, $4.073\times 10^{-19}J$

Answer 2

E = hf

c = speed of electromagnetic wave, c ≈ 3 * 10⁸ m/s, 
Planck's constant h = 6.63 *10⁻³⁴ Js

h = Planck's constnat,  Frquency, f = c/λ = (3*10⁸)/(488*10⁻⁹)

E = hf

E = hc/λ

E = (6.63 * 10⁻³⁴ * 3 * 10⁸) /(488 * 10⁻⁹)

Energy, E ≈ 4.0758 * 10⁻¹⁹  Joules.