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JEE Mains · Physics · STD 12 - Dual nature of radiation and matter
- JEE Mains 2017
- Medium
- MCQ
A Laser light of wavelength \(660\,nm\) is used to weld Retina detachment. If a Laser pulse of width \(60\, ms\) and power \(0.5\, kW\) is used the approximate number of photons in the pulse are : [Take Planck's constant \(h\, = 6.62\times10^{- 34}\, Js\)]
Pick an option to check your answer.
Answer & Solution
Correct Answer
(A) \(10^{20}\)
Step-by-step Solution
Detailed explanation
Given, \(\lambda=660 \mathrm{nm}, \text { Power }=0.5 \mathrm{kW}, \mathrm{t}=60 \mathrm{ms}\)
Power \(P=\frac{\text { nhc }}{\lambda t} \Rightarrow n=\frac{p \lambda t}{h c}\)
\(=0.5 \times 10^{3} \times \) \(\frac{{660 \times {{10}^{ - 9}} \times 60 \times {{10}^{ - 3}}}}{{6.6 \times {{10}^{ - 34}} \times 3 \times {{10}^8}}}\)
\(=100 \times 10^{18}=10^{20}\)
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