Question

Find the energy of the following. Express your answers in units of electron volts, noting that 1 eV = 1.60 10^-19 J.

(a) a photon having a frequency of 6.20 10¹⁷ Hz
eV

(b) a photon having a wavelength of 2.20 10² nm
eV

Answer 1

Solution :

Given : 1 eV = 1.60 10^-19 J

Since : Energy of photon is given by :

Part (a) Solution :

Here, f = 6.20 10¹⁷ Hz

Thus : E = h f = (6.626 x 10^-34 Js)(6.20 10¹⁷ Hz) = 41.0812 x 10^-17 J = 2.57 x 10³ eV  

Part (b) Solution :

Here, = 2.20 x 10² nm = 2.20 x 10^-7 m

Thus : E = hc/ = (6.626 x 10^-34 Js)(3 x 10⁸ m/s) / (2.20 x 10^-7 m) = 9.035 x 10^-19 J = 5.647 eV