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 \( h = 6.6 \times 10^{-34} \text{ Js} \))
- A \( 2.5 \times 10^{21} \)
- B \( 4.5 \times 10^{21} \)
- C \( 4.5 \times 10^{24} \)
- D \( 5.5 \times 10^{21} \)
Answer & Solution
Correct Answer
(B) \( 4.5 \times 10^{21} \)
Step-by-step Solution
Detailed explanation
\( N = \frac{P \times t \times \lambda}{hc} \) \( N = \frac{25 \text{ W} \times 60 \text{ s} \times 6000 \times 10^{-10} \text{ m}}{6.6 \times 10^{-34} \text{ Js} \times 3 \times 10^8 \text{ m/s}} \) \( N \approx 4.5 \times 10^{21} \)
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