The wavelength and power of the incident light is 4000 Å and 0.1 W respectively. The number of incident photons is _____.

Q.1 (x) The wavelength and power of the incident light is 4000 Å and 0.1 W respectively. The number of incident photons is _____.

A. \(2.011\times10^{17}\)

B. \(3.011\times10^{17}\)

C. \(4.011\times10^{17}\)

D. \(5.011\times10^{17}\)

Doubtly Asked 28 Oct 2026 Board exam · July 2025 hsc 12th Save WhatsApp Report

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Answer: A. \(2.011\times10^{17}\)

Answer: (a) \(2.011\times10^{17}\) (per second)

\[n = \frac{P\lambda}{hc} = \frac{0.1\times4\times10^{-7}}{6.63\times10^{-34}\times3\times10^{8}} = \frac{4\times10^{-8}}{1.989\times10^{-25}} = 2.011\times10^{17}\ \text{photons/s}\]

Doubtly AI · 28 Oct 2026 AI-verified · Oct 2026 Report

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The wavelength and power of the incident light is 4000 Å and 0.1 W respectively. The number of incident photons is _____.

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