If the wavelength of an electromagnetic radiation is doubled, the energy of the photons would be

one half of its initial value

The correct answer is Option (3) → one half of its initial value

Energy of a photon is given by the formula:

$E = \frac{hc}{\lambda}$

Here, $h$ is Planck's constant, $c$ is the speed of light, and $\lambda$ is the wavelength.

If the wavelength is doubled, i.e., $\lambda$ becomes $2\lambda$, then the new energy becomes:

$E' = \frac{hc}{2\lambda} = \frac{E}{2}$

So, doubling the wavelength reduces the energy of each photon to half its original value.