Question

For refraction at a curved surface, identify the wrong statement in accordance with the curved surface formula.

• A. ${\mu }_2$ is the refractive index of the medium, in which the refraction takes place.
• B. ${\mu }_1$ is the refractive index of the medium, from where the light is incident on the surface.
• C. R is the radius of curvature of the refractive surface.
• D. R is always positive.

Answer 1

The correct option is D R is always positive.

The curved surface formula is,
$\frac{{\mu }_2}{v}-\frac{{\mu }_1}{u}=\frac{{\mu }_2-{\mu }_1}{R}$
where:
${\mu }_2:$ Refractive index of the medium in which the refraction takes place
${\mu }_1:$ Refractive index of the medium, from where the light is incident on the surface
$R:$ Radius of curvature of the surface.

R can be positive or negative depending on the refracting surface. Assuming that the light is travelling from the left, if the refracting surface is concave, the value is negative and if it is convex the value if positive.