$A$ $60 \,W$ source emits monochromatic light of wavelength $662.5 \,nm$. The number of photons emitted per second is

The value of Planck's constant is

$A$ photon of wavelength $\lambda$ is scattered from an electron,which was at rest. The wavelength shift $\Delta \lambda$ is three times of $\lambda$ and the angle of scattering $\theta$ is $60^o$. The angle at which the electron recoiled is $\phi$. The value of $\tan \phi$ is: (electron speed is much smaller than the speed of light)

Given below are two statements:
Statement-$I$: Two photons having equal linear momenta have equal wavelengths.
Statement-$II$: If the wavelength of a photon is decreased,then the momentum and energy of the photon will also decrease.
In the light of the above statements,choose the correct answer from the options given below.

If the emitted radiation falls in the microwave region,the device is termed as

Two sources of light emit with a power of $200 \ W$. The ratio of the number of photons of visible light emitted per second by each source having wavelengths $300 \ nm$ and $500 \ nm$ respectively,will be: