(i) Name the type of a diode whose characteristics are shown in figure (1) and figure (2).
(ii) What does the point P in figure (1) represent?
(iii) What does the points P and Q in figure (2) represent?

Explanation

Figure-1 is the characteristics of zener diode and figure-2 is the characteristics of solar cell.
(ii) Point P in figure-1, indicates reverse voltage at zener breakdown (which is also known as zener voltage).
(iii) Point P in figure-2, indicates such positive voltage on the solar cell, current obtained due to which is equal and opposite to current obtained by the incidence of light on solar cell. Hence, resultant current passing through solar cell becomes I = 0. Such voltage is called "open circuit voltage".
Point O in figure-2 indicates the current obtained in solar cell when light with frequency equal to threshold frequency is made incident on it, when voltage applied to solar cell by the battery is zero. This current is opposite to current sent by the battery. Such current is known as "short circuit current".