Question

The photoelectric effect proves that light consists of
A. Photons
B. Electrons
C. Electromagnetic waves
D. Mechanical waves

Answer 1

We know that when electrons are ejected from the surface of a metal when light is incident on it, the process known as photoelectric effect. The electrons which are ejected, called photoelectrons. Thus, to solve this question, we need to understand the concept of this photoelectric effect.

Complete answer:
The photoelectric can be explained by the particle nature of light, in which light can be considered as a stream of particles of electromagnetic energy. These particles of light are called photons. The energy of this photon is given by:
$E = hv = \dfrac{{hc}}{\lambda }$
where, $E$ is the energy of the photon, $h$ is the Planck’s constant, $v$ is the frequency of the light, $c$ is the speed of light and $\lambda$ is the wavelength of the light.
Thus, it is clear that different frequencies of light carry photons of different energies.Therefore, it can be concluded that the photoelectric effect proves that light consists of photons.

Hence, option A is the right answer.

Note: We have seen that different frequencies of light carry photons of different energies. For instance, the frequency of blue light is more than that of red light. We can also say that the wavelength of blue light is much lower than the wavelength of red light. Therefore, it is clear that the energy held by a photon of blue light will be higher than the energy held by a photon of red light.