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Calculate the number of photons emitted per second when λ = 667 × 10^-9 m and P = 9 × 10^-3 W.

1. P = Nhc/λ, N = No. of photons emitted/sec.
2. N = 9 × 10^-3 × 667 × 10^-9 / 6.6 × 10^-34 × 3 × 10^8
3. N = 3 × 6.6 × 10^-26 / 3 × 10^-16 /sec
4. N = 3 × 10^16 photons/sec

Correct answer: N = 3 × 10^16 photons/sec

Solution

The energy of a single photon is given by E = hc/λ. The number of photons emitted per second, N, is calculated as P/E. Substituting the given values, N = Pλ/hc = (9 × 10^-3 × 667 × 10^-9) / (6.6 × 10^-34 × 3 × 10^8) = 3 × 10^16 photons/sec.

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