Question

A source of monochromatic light liberates 9 × 10²⁰ photon per second with wavelength 600 nm when operated at 400 W. The number of photons emitted per second with wavelength of 800 nm by the source of monochromatic light operating at same power will be:

Options

• 12 × 10²⁰

• 6 × 10²⁰

• 9 × 10²⁰

• 24 × 10²⁰

Answer 1

12 × 10²⁰

Explanation:

As we know

I =`"E"/"At"="nhv"/"At"`

⇒ `"n"/"t" = ("IA"lambda)/"hC"`

⇒ `"n"/"t"=(rholambda)/"hc"` 

⇒ `"n"/"t" = rholambda`

⇒ `("n"/"t")_2 =("n"/"t")_1xx("p"_2lambda_2)/("p"_1lambda_1)`

= `9xx10^20xx"P"/"P"xx800/600`

= 12 × 10²⁰