Question

what is spontaneous emissions of radiation

Answer 1

if electron orbiting get energy any manner get excited state that get lower to higher orbit this state is not stable so it sate at state for about 10^-8 second and emittes energy that extra energy come back to ground state this emitted energy is called spontaneous emission of radiation

Answer 2

Hay friend!
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Spontaneous emission is the process in which a quantum mechanical system ( such as an atom , molecule and a subatomic particle ) transition from an existed energy state to a lower energy state and emits a quantum in the form of a Photon .In Spontaneous emission of radiation an incoming Photon of a specific frequency can interacted with an existed atomic electron .

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