Two monochromatic beams $A$ and $B$ of equal intensity $I$ hit a screen. The number of photons hitting the screen by beam $A$ is twice that by beam $B$. What inference can you make about their frequencies?

Which of the following statements is $NOT$ true?

$A$ photon is associated with .........

Estimating the following two numbers should be interesting. The first number will tell you why radio engineers do not need to worry much about photons! The second number tells you why our eye can never 'count photons',even in barely detectable light.
$(a)$ The number of photons emitted per second by a Medium wave transmitter of $10\; kW$ power,emitting radiowaves of wavelength $500\; m$.
$(b)$ The number of photons entering the pupil of our eye per second corresponding to the minimum intensity of white light that we humans can perceive $(10^{-10}\; W m^{-2})$. Take the area of the pupil to be about $0.4\; cm^2$,and the average frequency of white light to be about $6 \times 10^{14}\; Hz$.

Consider a hypothetical annihilation of a stationary electron with a stationary positron. What is the wavelength of the resulting radiation? ($h =$ Planck's constant,$c =$ speed of light,$m_0 =$ rest mass)

If the energy of the photon is increased by a factor of $4$,then its momentum