All exercise S.Qs of Chapter#3: Time Dependent Perturbation Theory of Quantum Mechanics-II. We have arranged all S.Qs for BS/MSc Physics students.
Q.3.1 why transition probability at act as absorption for harmonic perturbation?
Answer:
The perturbation can induce transitions from Ei only to a level Ef whose energy is higher than EI by just . Such a transition may be described as absorption energy by the system.
Q.3.2 why energy is conserved in in constant perturbation?
Answer: The delta term guarantees the conservation of energy: in the limit , the transition rate is non-vanishing only between states of equal energy. Hence, a constant (time independent) perturbation neither removes energy from the system nor supplies energy to it. It simply causes energy-conserving transitions.
Q.3.3 what is the time period of transition probability of oscillating sinusoidal function?
Answer:
Or
This is time period.
Q.3.4 why absorption and emission process cannot take place simultaneously?
Answer: The absorption and emission are inverse process.
Absorption process:
When atoms absorbs energy of photon to promote electron to higher energy orbital;
Emission process:
When atoms emits energy as photon as electron falls from higher energy orbital to lower;
Q.3.5 wrote down necessary conditions for the existence of Pif for a harmonic perturbation.
Answer: The transition rate
The first condition is called emission.
The second condition is called absorption.
Q.3.6 why transition probability has an interference pattern?
Answer: As a function of , the transition probability has an interference pattern. It is appreciable only near and decays moves away from zero.
Q.3.7 Define MASER and LASER.
Answer: MASER: (Microwave amplification by stimulated emission of radiation).
LASER: (Light amplification by stimulated emission of radiation).