Question

When a biconvex lens of glass having refractive index $1.47$ is dipped in a liquid, it acts as a plane sheet of glass. This implies that the liquid must have refractive index

• A. equal to that of glass
• B. less than one
• C. greater than that of glass
• D. less than that of glass

Answer 1

Answer: (A)

equal to that of glass

Answer 2

$\frac{1}{ f }=\left(\frac{\mu_{2}}{\mu_{1}}-1\right)\left(\frac{1}{ R _{1}}-\frac{1}{ R _{2}}\right)$
For power $=\frac{1}{ f }=0,\, \mu_{2}=\mu_{1}$