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LoginAtomic lithium of concentration n=3.6.10^(16)cm^(-3) is at a temperature T=1500K. In this case the power emmitted at the resonat line's wavelength lambda=671nm(2Prarr 2S) per unit volume of gas is equal to P=0.30W//cm^(3). Find the mean lifetime of Li atoms in the resonance excitation state.
Class 12 Physics in Class 12 3 years ago
`N=n(g_(p))/(g_(s))e^(-2pi hc//lambda kT)`
Here `g_(p)=` degeneracy of the 2p state`=6,g_(s)=` degeneacy of the `2s` state`=2` and `lambda=` WAVELENGTH of the resonant line `2p rarr 2s`. The rate of decay of these atoms is `(N)/(TAU)` per sec. per unit volume, since each such atom EMITS light of wavelength `lambda`, we MUST have
`(1)/(tau)(2pi ħc)/(lambda)n(g_(p))/(g_(s))e^(-2pi h c//lambda kT)=P`
Thus `tau=(1)/(P)`
Thus `tau=(1)/(P)(2pi ħc)/(lambda)n(g_(p))/(g_(s))e^(-2pi h c//lambdakT)=65.4xx10^(-9)s=65.4ns`
Posted on 11 Dec 2021, this text provides information on Class 12 related to Physics in Class 12. Please note that while accuracy is prioritized, the data presented might not be entirely correct or up-to-date. This information is offered for general knowledge and informational purposes only, and should not be considered as a substitute for professional advice.
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