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

According to the photon theory of light,which of the following physical quantities associated with a photon does not change as it collides with an electron in a vacuum?

The energy of a photon with a wavelength of $\lambda = 4000 \ \mathring{A}$ is equal to ........ Joules.

The fact that photons carry energy was established by

Calculate the number of photons entering the eye of a duck per second,corresponding to the minimum intensity of white light $(\sim 10^{-10} \ W/m^2)$. Take the area of the duck's eye as $0.4 \ cm^2$ and the average frequency of white light as $6 \times 10^{14} \ Hz$.

$A$ photon of frequency $v$ has a momentum associated with it. If the speed of light is $c$,then the momentum is .......