Question

For the wave of light you generated in the Part B, calculate the amount of energy in 1.0 mol of photons with that same frequency (6.8×109 Hz ) and wavelength (0.044 m ). Recall that the Avogadro constant is 6.022×1023 mol−1. Express the energy in joules to two significant figures.

Answer 1

2.7 J

Step-by-step explanation:

The energy of one photon is given by

`E=hf`

where

h is the Planck constant

f is the frequency

For the photons in this problem,

`f=6.8\cdot 10^9 Hz`

So the energy of one photon is

`E_1=(6.63\cdot 10^(-34))(6.8\cdot 10^9 )=4.5\cdot 10^(-24) J`

The number of photons contained in 1.0 mol is

`N_A = 6.022\cdot 10^(23) mol^(-1)` (Avogadro number)

So the total energy of
`N_A` photons contained in 1.0 mol is

`E=N_A E_1 =(6.022\cdot 10^(23))(4.5\cdot 10^(-24))=2.7 J`