Lens Maker's Formula — MCQ Practice

A biconvex lens made of glass (refractive index $n_L = 1.5$) has radii of curvature $R_1 = 20,\text{cm}$ and $R_2 = -30,\text{cm}$. What is its focal length when placed in air (refractive index $n_m = 1$)?

A plano-convex lens has a refractive index of $1.6$ and the radius of curvature of its curved surface is $15,\text{cm}$. What is its focal length in air?

A convex lens has a focal length of $20,\text{cm}$ in air. If the refractive index of the lens material is $1.5$, what will be its focal length when immersed in water (refractive index $1.33$)?

A biconcave lens has radii of curvature $10,\text{cm}$ and $15,\text{cm}$. If its focal length in air is $-12,\text{cm}$, what is the refractive index of the lens material?

A lens is made of a material with refractive index $n_L = 1.5$. It is placed in a medium with refractive index $n_m = 1.6$. If the lens is biconvex with radii of curvature $R_1 = 10,\text{cm}$ and $R_2 = -10,\text{cm}$, what will be its nature and focal length?

Which of the following statements about the Lens Maker's Formula is INCORRECT?

A biconvex lens made of material with refractive index $1.5$ has equal radii of curvature of $20,\text{cm}$. What is the power of this lens in diopters when placed in air?