Monochromatic light of frequency 6.0 x 10¹⁴ Hz is produced by a laser. The power emitted is 2 x 10⁻³ ?. The number of photons emitted, on the average, by the sources per second is

Options

(a) 5 x 10¹⁶
(b) 5 x 10¹⁷
(c) 5 x 10¹⁴
(d) 5 x 10¹⁵

Correct Answer:

5 x 10¹⁵

Explanation:

Since P = nhv
n = p/hv = 2 x 10⁻³ / 6.6 x 10⁻³⁴ x 6.0 x 10¹⁴
= 5 x 10¹⁵