Given:
Wavelength (λ) of the laser pulse = 545 nm = 5.45 * 10⁻⁹ m
Total energy of pulse = 4.85 mJ
To determine:
The number of photons in the laser of a given energy
Explanation:
Energy per photon (E) = hc/λ
where h = planck's constant = 6.626 *10⁻³⁴ Js
C = speed of light = 3*10⁸ m/s
λ = wavelength
E = 6.626 *10⁻³⁴ Js* 3*10⁸ms-1 /5.45 * 10⁻⁹ m = 3.65 * 10⁻¹⁹ J
Now,
# photons = total energy/Energy per photon
= 4.85 * 10⁻³ J* 1 photon / 3.65 * 10⁻¹⁹ J = 1.32 * 10¹⁶ photons
Ans: the laser pulse contains 1.32 * 10¹⁶ photons
