Question

Monochromatic light of frequency is 6.0 × 10¹⁴ Hz produced by a laser. The power emitted is 2 × 10^–3 W. The number of photons emitted, on the average, by the source per second is
1. 5 × 10¹⁴
2. 5 × 10¹⁵
3. 5 × 10¹⁶
4. 5 × 10¹⁷

Answer 1

Correct Answer - Option 2 : 5 × 10¹⁵

CONCEPT:

The power of a photoelectric effect source is the product of the number of electrons times the energy of each electron and is given by

⇒ P= nE

Where n = number of electrons,E = Energy of each photon

CALCULATION:

Given - ν = 6 × 1014 Hz, and Power = 2 × 10–3 W

The power of the photoelectric source is given by P = nE

\(\Rightarrow n = \frac{P}{E} = \frac{P}{hν}\)       [∵ E = hν]

\(n =\dfrac{2 \times 10^{-3}}{6.626\times 10^{-34} \times 6 \times 10^{14}} = 5.03\times 10^{15}\)

Hence, option 2 is the answer