Q. A hydrogen atom is in the $4^{th}$ excited state, then:

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A

the maximum number of emitted photons will be 10

B

the maximum number of emitted photons will be 6

C

it can emit three photons in ultraviolet region

D

if an infrared photon is generated, then a visible photon may follow this infrared photon

Solution:

The hydrogen atom is in $n = 5$ state.
Thus maximum number of possible photons $={ }^{5} C_{2}=10$.
To emit photon in ultra violet region, it must jump to $n=1$, because only Lyman series lies in UV region.
Once it jumps to $n=1$ photon, it reaches to its ground state and no more photons can be emitted.
So only one photon in $u. v.$ range can be emitted.
If $H-$atom emits a photon and then another photon of Balmer series, option D will be correct.

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