A photographic flash capacitor stores of electrical energy and discharges it in

PHYSICS · Single correct · A Level · Physics · Particles and radiation · Particles and radiation

Problem

A photographic flash capacitor stores

40\,\text{J}

of electrical energy and discharges it in

0.020\,\text{s}

. Only

15\%

of this energy becomes light, and of that light,

70\%

is emitted as monochromatic green photons of wavelength

525\,\text{nm}

. What is the average emission rate of these green photons during the flash? (a)

7.9\times10^{20}\,\text{photons s}^{-1}

(b)

5.6\times10^{20}\,\text{photons s}^{-1}

(c)

1.1\times10^{19}\,\text{photons s}^{-1}

(d)

3.7\times10^{21}\,\text{photons s}^{-1}