A liquid is exposed to infrared radiation with a wavelength of 6.61×10−4 cm.

Question

Assume that all the radiation is absorbed and converted to heat. How many photons are required for the liquid to absorb 45.33 J of heat?

Answer 1

E = hc/λ

E = energy of a photon

h = Plancks constant = 6.626x10^-34 Jsec

c = speed of light = 3x10⁸ m/sec

λ = wavelength in m = 6.61x10^-4 cm x 1 m/10² cm = 6.61x10^-6 m

E = (6.626x10^-34 Jsec)(3x10⁸ m/sec) / 6.61x10^-6 m

E = 3.00x10^-20 J = 3.00x10^-23 kJ

No. photons required:

45.33 kJ x 1 photon / 3.00x10^-23 kJ = 1.51x10²² photons