A liquid is exposed to infrared radiation with a wavelength of 9.70×10−4 cm.

Question

Assume that all the radiation is absorbed and converted to heat. How many photons are required for the liquid to absorb 38.64J of heat?

Answer 1

E = hc / λ

E = energy of 1 photon = ?

h = Plank's constant = 6.626x10^-34 J-sec

c = speed of light ~ 3x10⁸ m/sec

λ = wavelength in m = 9.70x10^-4 cm x 1 m / 100 cm = 9.70x10^-6 m

E = (6.626x10^-34 J-sec)(3x10⁸ m/sec) / 9.70x10^-6 m

E = 5.46x10^-20J

38.64 J x 1 photon / 5.46x10^-20 J = 7.08x10²⁰ photons