Question

A monochromatic source of light operating at 200 W emits $4\times {10}^{20}$ photons per second. Find the wavelength of the light $(in\times {10}^{-7}m)$

Answer 1

We know that , Power = (Number of photons per second ) $\times$ $\frac{hC}{\lambda }$
200 = $4\times {10}^{20}\times \frac{2\times {10}^{-25}}{\lambda }$
$\therefore \lambda$ = 4$\times {10}^{-7}$ m