Question

What is the energy output of a light source in J/s (joules per second) if it produces 324 photons per second, and these photons have a wavelength of 143 nm? c = 2.998 x 108 m/s. h = 6.63 x 10-34 J-s. a) The energy output is 1.39e-18 J/s. b) The energy output is 4.50e-16 J/s. c) The energy output is 2.33e+20 J/s. d) The energy output is 4.29e-21 J/s. e) The energy output is 3.07e-38 J/s.

Answer 1

Answer:

b) The Energy Output is 4.50e-16 J/s

Explanation:

From Plank's Law:

E = n h υ

where,

E = Total Energy

n = No. of Photons = 324 /sec

h = 6.63 x 10⁻³⁴ J.sec

υ = frequency of light = speed of light / Wavelength

υ =  (2.998 x 10⁸ m/s)/(143 x 10⁻⁹ m)

υ = 2.096 x 10¹⁵ /sec

Therefore,

E = (324 /sec)(6.63 x 10⁻³⁴ J.sec)(2.096 x 10¹⁵ /sec)

E = 45.03 x 10⁻¹⁷ J/s

E = 4.50 x 10⁻¹⁶ J/s

Hence, the correct answer is:

b) The Energy Output is 4.50e-16 J/s