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CUET · PHYSICS · PYQ PAPER 2023

A monochromatic source emitting light of wavelength 300 nm has a power output of 33 W.
Calculate the number of photons emitted by this source in 2 minutes. (\( h = 6.62 \times 10^{-34} \text{ J s} \))

  1. A \( 6 \times 10^{21} \)
  2. B \( 4.2 \times 10^{20} \)
  3. C \( 3.8 \times 10^{24} \)
  4. D \( 1.6 \times 10^{19} \)
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Answer & Solution

Correct Answer

(A) \( 6 \times 10^{21} \)

Step-by-step Solution

Detailed explanation

\( E = \frac{hc}{\lambda} = \frac{(6.62 \times 10^{-34} \text{ J s}) \times (3 \times 10^8 \text{ m/s})}{300 \times 10^{-9} \text{ m}} = 6.62 \times 10^{-19} \text{ J} \) \( E_{total} = P \times t = 33 \text{ W} \times (2 \times 60 \text{ s}) = 3960 \text{ J} \)…
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