Answer:
λ=384 nm
Explanation:
Given an atom in normal state absorbed a photon and gone into excited state then again it returns to the normal state by emitting two photons of wavelength 675 nm and 1350 nm
We know that
The energy absorbed = The energy emitted
The energy absorbed / emitted by an atom = [tex]\frac{hc}{z}[/tex]
Let z be the wavelength of the recquired photon and [tex]z_{1}[/tex]=675 be the wavelength of the first photon and [tex]z_{2}[/tex]=1350 be the wavelength of the second photon.
Now
[tex]\frac{hc}{ z} =\frac{hc}{z1} +\frac{hc}{z2}[/tex]
[tex]\frac{1}{z} =\frac{1}{z1} +\frac{1}{z2 }[/tex]
[tex]\frac{1}{z} =\frac{1}{675} +\frac{1}{1350 }[/tex]
[tex]\frac{1}{z} =\frac{1350+675}{1350\times 675}[/tex]
[tex]\frac{1}{z} =\frac{2025}{777600}[/tex]
z=[tex]\frac{777600}{2025}[/tex]
z=384 nm