Question

A stellar object is emitting radiation at 1770 nm. A detector is capturing 7 107 photons per second at this wavelength. h = 6.63 x 10-34 J-s. c = 2.998 x 108 m/s. (a) What is the total energy of the photons detected in one second? J/s (b) What is the total energy of the photons detected in one hour? J/hr

Answer 1

a) E = nhv = nhc/ λ

h = planck's constant = 6.625 x 10^-34 J.s

c = velocity of light = 3 x 10 ⁸ m/s

λ= wavelength = 1770 nm = 1770 x 10^-9 m

n = no of photons per second= 7107

Hence,

  E = hc / λ

= (7107) (6.626 x 10^-34 J.s) (3 x 10⁸ m/s) / (1770 x 10^-9 m)

= 79.81 x 10^-17 J

E =   79.81 x 10^-17 J

b)

h = planck's constant = 6.625 x 10^-34 J.s

c = velocity of light = 3 x 10 ⁸ m/s

λ= wavelength = 1770 nm = 1770 x 10^-9 m

n = no of photons per hour = 7107 x 3600

Hence,

  E = hc / λ

= (7107x 3600) (6.626 x 10^-34 J.s) (3 x 10⁸ m/s) / (1770 x 10^-9 m)

= 287316 10^-17 J

E = 287316 x 10^-17 J