Calculate the number of photons emitted by a `100 W` yellow lamp in `1.0 s`. Take the wavelength of yellow light as `560 nm` and assume `100` percent efficiency.

Options

A. `6.8xx10^(20)`
B. `4xx10^(12)`
C. `4xx10^(20)`
D. `2.8xx10^(20)`

Answer

4

Explanation

The number pf photon is `N=E/(hv)=(PDeltat)/(h(c//lambda))=(lambdaPDeltat)/(hc)`
Substitution of the data gives
`N=((5.60xx10^(-7)m)xx(100Js^(-1))xx(1.0s))/((6.626xx10^(-36)s)xx(3xx10^(8)ms^(-1)))=2.8xx10^(20)`