A p-n junction has a built-in potential of 0·8 V. The depletion

A p-n junction has a built-in potential of 0·8 V. The depletion layer width at a reverse bias of 1·2 V is 2 µm. For a reverse bias of 7·2 V, the depletion layer width will be—

We know that depletion layer width and reverse bias voltage are related by expression

d α		1 +	V_r		^{1 / 2}
			V_B

Where,
d = depletion
width V_r = applied reverse bias voltage
V_B = built in potential

Now,		d₁	=	V_B + V_R1
		d₂		V_B + V_R2

or d₂ =	V_B + V_R2	^{1 / 2}× d₁
	V_B + V_R1

or d₂ =		0·8 + 7·2		^{1 / 2}× µm
		0·8 + 1·2

or d₂ =		8		^{1 / 2}× 2µm = 4µm
		2

Hence alternative (A) is the correct choice.