Question

Two refracting media are separated by a spherical interface as shown in figure. PP' is the principle axis. ${\mu }_1$and ${\mu }_2$ are the refractive indices of medium of incidence and medium of refraction respectively. Then:

• A. If ${\mu }_2>{\mu }_1$ ,then there cannot be a real image of real object.
• B. If ${\mu }_2>{\mu }_1$ ,then there cannot be a real image of virtual object.
• C. If ${\mu }_1>{\mu }_2$ ,then there cannot be a virtual image of virtual object
• D. If ${\mu }_1>{\mu }_2$,then there cannot be a real image of real object

Answer 1

Answer: (A), (C)

The correct options are
A If ${\mu }_2>{\mu }_1$ ,then there cannot be a real image of real object.
C If ${\mu }_1>{\mu }_2$ ,then there cannot be a virtual image of virtual object

We use the lens formula involving 2 refractive media,

$\frac{{\mu }_2}{V}-\frac{{\mu }_1}{u}=\frac{{\mu }_2-{\mu }_1}{R}$

Now, R is always negative.

Case 1 : ${\mu }_2>{\mu }_1$ and U < 0 (Real object)

V cannot be negative. Thus, the image can never be real.

Case 2 : ${\mu }_2<{\mu }_1$ and U > 0 (Virtual object)

V can never be +ve, thereby a virtual image can never form