(N/A) From the photoelectric effect and Compton effect,the characteristics of a photon can be represented as follows:
$(1)$ During the interaction of radiation with matter,radiation behaves as a particle,which is called a photon.
$(2)$ The energy of each photon is $E = h\nu$ and the momentum of each photon is $p = \frac{h\nu}{c}$.
$(3)$ In a vacuum,the speed of a photon is equal to the speed of light $(c)$.
$(4)$ If $\lambda$ is the wavelength of the radiation and $\nu$ is the frequency of the photon,then the energy of each photon is $E = h\nu = \frac{hc}{\lambda}$ and the momentum is $p = \frac{h\nu}{c} = \frac{h}{\lambda}$. This is independent of intensity.
$(5)$ According to photon theory,if $n$ photons are incident on a unit area per unit time,then the intensity of light $I = nh\nu$,where $h\nu$ is the energy of $1$ photon and $\nu$ is the frequency of the incident light. The energy of a photon does not depend on the intensity of the radiation.
$(6)$ Photons are electrically neutral. They do not get deflected by electric or magnetic fields.
$(7)$ During a photon-particle collision (e.g.,electron-photon collision),total energy and total momentum are conserved. Sometimes,the number of photons may not be conserved,or new photons may be produced.
$(8)$ The effective mass of a photon is $m = \frac{h\nu}{c^2}$. According to Einstein's theory of relativity,$E = mc^2$,therefore $h\nu = mc^2$,which implies $m = \frac{h\nu}{c^2}$.