Which one of the following statements is not correct?

Statement 2 is incorrect because the power of a lens is the reciprocal of its focal length (P = 1/f) [4]. According to standard sign conventions, the focal length of a convex (converging) lens is positive, while the focal length of a concave (diverging) lens is negative [2]. Consequently, the power of a convex lens is positive and that of a concave lens is negative [2]. Statement 1 is correct as the radius of curvature (R) is twice the focal length (f), expressed as R = 2f [3]. Statement 3 is correct because a plane mirror is considered a spherical mirror with an infinite radius of curvature [3]. Statement 4 is correct because light travelling from an optically denser medium to a rarer medium bends away from the normal, making the angle of refraction greater than the angle of incidence [1].

Sources

1. [4] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.8 Power of a Lens > p. 157
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.6 Sign Convention for Spherical Lenses > p. 155
3. [1] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > What you have learnt > p. 159
4. [3] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > Activity 9.2 > p. 137