The magnitudes of power of a biconvex lens (refractive index 1.5) and… | JEE Main 2026 (28 Jan, Shift 1)

Q9JEE Main 2026 · 28 JAN · SHIFT 1Medium

Spherical Surfaces & Thin Lenses

The magnitudes of power of a biconvex lens (refractive index 1.5) and that of a plano-concave lens (refractive index $= 1.7$ ) are same. If the curvature of planoconcave lens exactly matches with the curvature of back surface of the biconvex lens, then ratio of radius of curvature of front and back surface of the biconvex lens is ______

Show answer and solution

Answer: (b)

Biconvex (front $R_1$ , back $R_2$ ): $P_1 = 0.5\left(\frac{1}{R_1} + \frac{1}{R_2}\right)$ .
Plano-concave with radius $R_2$ : $|P_2| = \frac{0.7}{R_2}$ .
$\frac{0.5}{R_1} + \frac{0.5}{R_2} = \frac{0.7}{R_2} \Rightarrow \frac{0.5}{R_1} = \frac{0.2}{R_2}$
$\frac{R_1}{R_2} = \frac{0.5}{0.2} = \frac{5}{2}$
So the answer is (b) $5 : 2$ .

Report a mistake

More questions on Spherical Surfaces & Thin Lenses

If sunlight is focused on a paper using convex lens, it starts burning the paper in…JEE Main 2026 (2 Apr, Shift 2)
The focal length of a glass convex lens in air is fa and that in water is fw. The…MHT CET 2026 (20 May, Shift 1)
Refractive index of a glass convex lens is 1.5. The radius of curvature of each of the…MHT CET 2026 (18 Apr, Shift 2)
A lens of refractive index ' μ ' has focal length ' f '. When the lens is immersed in a…MHT CET 2026 (17 Apr, Shift 1)
A convex lens having refractive index 1.6 has focal length 12 cm, when it is in air. The…MHT CET 2026 (16 Apr, Shift 2)
A convex lens of refractive index 1.5 and focal length f = 18 cm is immersed in water…JEE Main 2026 (28 Jan, Shift 1)
Refer the figure given below. μ₁ and μ₂ are refractive indices of air and lens material…JEE Main 2026 (2 Apr, Shift 1)
Five persons P₁, P₂, P₃, P₄ and P₅ recorded object distance (u) and image distance (v)…JEE Main 2026 (24 Jan, Shift 2)

Spherical Surfaces & Thin Lenses question from JEE Main 2026 (28 Jan, Shift 1)

More questions on Spherical Surfaces & Thin Lenses