Calculate the number of photons emitted per second by a $10$ watt sodium vapour lamp. Assume that $90$ % of the consumed energy is converted into light. Wavelength of sodium light is $590 n m, h = 6.63 \times 10^{- 34} J s$ .

2.67 \times 10^{17}

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2.67 \times 10^{18}

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2.67 \times 10^{19}

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2.67 \times 10^{20}

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Solution

The correct option is C $2.67 \times 10^{19}$ .
P = 10 W(given)

this means E in 1 sec = 10 J
% used to convert into photon = 90% (given)

∴ Energy used = 9 J

Energy used to take out 1 photon = hc/λ = 6.63* 10^-34 * 3 * 10⁸/590 * 10^-9 = 6.633/590 * 10^-17

No. of photons used = 9/6.63 3/590 10^-17
= 9* 590/6.63 * 310¹⁷
= 266.9 10¹⁷
= 2.67 * 10¹⁹

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Calculate the number of photons emitted per second by a 10 watt sodium vapour lamp. Assume that 90% of the consumed energy is converted into light. Wavelength of sodium light is 590 nm,h=6.63×10−34Js.

Calculate the number of photons emitted per second by a $10$ watt sodium vapour lamp. Assume that $90$ % of the consumed energy is converted into light. Wavelength of sodium light is $590 n m, h = 6.63 \times 10^{- 34} J s$ .