SELECT * FROM question_mgmt as q WHERE id=3185 AND status=1 SELECT id,question_no,question,chapter FROM question_mgmt as q WHERE courseId=2 AND subId=9 AND chapterId=51 and ex_no='1' AND status=1 ORDER BY CAST(question_no AS UNSIGNED)
Why are potassium and cesium, rather than lithium used in photoelectric cells?
All the three, lithium, potassium, and cesium, are alkali metals. Still, K and Cs are used in the photoelectric cell and not Li.
This is because as compared to Cs and K, Li is smaller in size and therefore, requires high energy to lose an electron. While on the other hand, K and Cs have low ionization energy. Hence, they can easily lose electrons. This property of K and Cs is utilized in photoelectric cells.
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