Tamilnadu BoardEnglish MediumSTD 11BIO BOTANYPhotosynthesis3 Marks
Question
Explain the term phosphorescence.
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Answer
Electron from Second Singlet State $\left( S _2\right)$ may return to next higher energy level $\left( S _1\right)$ by losing some of its extra energy in the form of heat. From first singlet state $\left(S_1\right)$ electron further drops to first triplet state $\left(T_1\right)$. Triplet State is unstable having half life time of $10^{-3}$ seconds and electrons returns to ground state with emission of light in red region called as phosphorescence. Phosphorescence is the delayed emission of absorbed radiations. Pathway of electron during Phosphorescence:
$S_2 \rightarrow S_1 \rightarrow T_1 \rightarrow S_0$
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