Answer:
The energy of photon is 2.26 eV
Step-by-step explanation:
It is given that,
A photon is emitted when an electron in a mercury atom falls to a lower energy level.
Frequency of photon,

We have to find the energy of this photon. Mathematically, the energy of the photon is given by :
E = h × f
Where h is the Planck's constant
We know that :

So,

E = 2.26 eV
So, the energy of this photon is 2.26 eV