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A bulb of 40 W is producing a light of w...

A bulb of 40 W is producing a light of wavelength 620 nm with `80%` of efficiency , then the number of photons emitted by the bulb in 20 seconds are :
(`1eV = 1.6 xx 10^(-19) J , hc = 12400 eV`)

A

`2xx10^(18)`

B

`10^(18)`

C

`10^(21)`

D

`2xx10^(21)`

Text Solution

Verified by Experts

The correct Answer is:
D
Power`=(nhC)/(lambdaxxt) rArr 40xx80/100=(nxx6.62xx10^(-34)xx3xx10^(8))/(620xx10^(-9)xx20) rArr n=2xx10^(21)`
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