A lens has a power of + 2.0 Dioptre, Which one of the following statements about the lens is true?

The power of a lens (P) is defined as the reciprocal of its focal length (f) in metres, expressed by the formula P = 1/f [2][3]. Given a power of +2.0 Dioptres, the focal length is calculated as f = 1/P = 1/2.0, which equals 0.5 metres [3]. According to standard sign conventions in optics, a positive power and a positive focal length indicate a convex (converging) lens, whereas a negative power and focal length indicate a concave (diverging) lens [3]. Therefore, a lens with a power of +2.0 Dioptres must be a convex lens with a focal length of 0.5 metres [3]. This relationship is fundamental in optometry for correcting vision defects like hypermetropia, which requires converging lenses [1].

Sources

1. [2] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > 9.3.8 Power of a Lens > p. 157
2. [3] 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 10: The Human Eye and the Colourful World > EXERCISES > p. 170