JEE MainPhysicsAtoms and NucleiMCQ+4 / −1
In Bohr's atomic model of hydrogen, let K, P and E are the kinetic energy, potential energy and total energy of the electron respectively. Choose the correct option when the electron undergoes transitions to a higher level :
- AAll K, P and E increase.
- BK decreases, P and E increase.
- CP decreases, K and E increase.
- DK increases, P and E decrease.
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Correct answer: B
- Write the Bohr model energy relations
For the electron in the th orbit of hydrogen:
Using the Coulomb-force/virial relation for Bohr orbit:
and
So:
- is positive and proportional to
- is negative and proportional to
- is negative and proportional to
- Consider transition to a higher level
A transition to a higher level means:
Hence,
Now check each quantity.
- Change in kinetic energy
Since
when increases, decreases.
So, kinetic energy decreases.
- Change in potential energy
Since
for higher , the value becomes less negative.
Example:
Clearly,
So, potential energy increases.
- Change in total energy
Since
for higher , the total energy also becomes less negative.
Example:
Thus,
So, total energy increases.
- Match with options
- decreases
- increases
- increases
Therefore, the correct option is:
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