Infrared lamps are used in restaurants to keep the food warm. The infrared radiation is strongly absorbed by water, raising is temperature and that of the food. If the wavelength of infrared radiation is assumed to be `1500nm`, then the number of photons per second of infrared radiation produced by an infrared lamp that consumes energy at the rate of `100W` and is `12%` efficient only is `y xx 10^(19)`. Find the value of `y`.

Options

A. 6
B. 7
C. 8
D. 9

Answer

4

Explanation

Power`=(En ergy)/(time)=((n)/(t))(hc)/(lambda)`
`100xx(12)/(100)=((n)/(t))xx(6.6xx10^(-34)xx3xx10^(8))/(1500xx10^(-9))`
So, `((n)/(t))=no`. of photons per second `=9xx10^(19)`