ExamBro
ExamBro
CUET · PHYSICS · PYQ PAPER 2025

The number of photons emitted per minute by a 25 W source of monochromatic light of wavelength \( 6000 \text{ \AA} \) is approximately: (take \( h = 6.6 \times 10^{-34} \text{ Js} \))

  1. A \( 2.5 \times 10^{21} \)
  2. B \( 4.5 \times 10^{21} \)
  3. C \( 4.5 \times 10^{24} \)
  4. D \( 5.5 \times 10^{21} \)
Verified Solution

Answer & Solution

Correct Answer

(B) \( 4.5 \times 10^{21} \)

Step-by-step Solution

Detailed explanation

\( N = \frac{P \times t \times \lambda}{hc} \) \( N = \frac{25 \text{ W} \times 60 \text{ s} \times 6000 \times 10^{-10} \text{ m}}{6.6 \times 10^{-34} \text{ Js} \times 3 \times 10^8 \text{ m/s}} \) \( N \approx 4.5 \times 10^{21} \)