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. `3xx10^(3)`
C. `1.4xx10^(-19)`
D. `3xx10^(4)`

Answer

A

Explanation

Energy radiated as vidible light is
`(5)/(100)xx100=5Js^(-1)`
Let n be the number of photons emitted per second. Then,
`(nhv)/(lamda)=5`
`n=(5lamda)/(hc)=(5xx5.6xx10^(-7))/((6.62xx10^(-34))(3xx10^(8)))`
`=1.4xx10^(19)`