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Monochromatic light of frequency 6 × 10 14 Hz is produced by a laser. The power emitted is 2 × 10 –3 W. How many photons per second on an average, are emitted by the source? (Given h = 6.63 × 10 –34 Js)

1. 6 × 10 15
2. 5 × 10 15
3. 7 × 10 16
4. 9 × 10 18

Correct answer: 5 × 10 15

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