1. A electromagnetic radiation is occurred when electron is coming back from 4 th state to its 2 nd state of an excited atom.
Mass of electron , charge of electron . Permitivity of constant at vacuum and Planck's constant . Range of visible light to .
2. An engine takes of heat from source at and rejects 700 of heat to the sink. By changing heat energy both of the source and the sink its efficiency can be increased through .
5.
Four diodes each of them are similar to diode in the figure-1 are connected as in the figure- 2 . In forward bias change of current occurred for the change of voltage to any one of the diode.