Question

According to Einstein’s theory, how does an increase in the number of photons affect a beam of light?

Answer 1

The answer is the third choice, "the brightness of the beam of light increases"

According to Einstein’s theory, an increase in the number of photons (per unit are) affects a beam of light by causing a higher intensity.  Sometimes, the term "brightness" is used when referring to the intensity of a color, although there are instances where this can be a misleading term when we try to describe intensity

Answer 2

Answer:

The brightness of the beam of light increases.

Explanation:

As per Einstein's experimental verification he proves that light is of particle nature and his equation for energy balance is given as

$h\nu = \phi + KE$

so incident photons on a photosensitive plate will eject the electrons from the plate with some sufficient KE.

So here light is considered as particles which means one photon will eject one electron. So here intensity of light is considered as

Intensity = (number of photons per second) (energy of one photon)

so it is given as

$I = \frac{N}{t}(\frac{hc}{\lambda})$

now if the intensity of light is increased for same wavelength of light then it means the number of photon must have to be increase.

so correct answer will be

The brightness of the beam of light increases.