If 5% of the energy supplied to a bulb is irradiated as visible light, how many quanta are emitted per second by a 100 W lamp? Assume wavelength of visible light as `5.6xx10^(-5)` cm.

Options

A. `1.4xx10^(19)`
B. `1.4xx10^(20)`
C. `2xx10^(19)`
D. `2xx10^(20)`

Answer

A

Explanation

`P=(5)/(100)xx100=5W`
`P=n(hc)/(lambda)`
`n=(P lambda)/(hc) =(5xx5.6xx10^(-7))/(6.6xx10^(-34)xx3xx10^(8)) =1.4xx10^(19)//sec`