Question

How do you calculate the number of photons having a wavelength of 10.0 micrometers required to produce 1.0 kilojoules of energy

Answer 1

To calculate this,

We know that energy is 1 photon 
E = hc/wavelenth 
wavelength of 10.0 m 

Solution:
h = 6.626 x 10^-34 Jsec 
C = 2.9979 x 10^8 m/sec 
E = 6.626 10^-34 * 2.9979 10^8 / 10 = 1.9864 10^-26J 

Then, the number of photons is computed by:

n = 1000 / 1.9864 10^-26 = 5.04 10^28 photons