RRB Group-D Model Paper 15 with answers for online practice

Concept:

• Photoelectric effect: When the light of a sufficiently small wavelength is incident on the metal surface, electrons are ejected from the metal instantly. This phenomenon is called the photoelectric effect.

Explanation

In the given options

• Sodium, lithium, and magnesium are electropositive and they also lose electrons easily but their reactivity is much less than Caesium.
•  Cesium is the most electropositive element of all so it has the minimum ionization energy and so contains the maximum capacity to lose electrons.