A lemon kept in water in a glass tumbler appears to be larger than its actual size. It is because of

A lemon kept in water in a glass tumbler appears larger than its actual size due to the refraction of light [1]. Refraction is the bending of light rays as they pass obliquely from one medium to another with a different optical density, such as from water to air. When light rays reflected from the lemon travel from the optically denser water into the less dense air, they bend away from the normal. Our eyes and brain perceive these refracted rays as traveling in a straight line, creating a virtual image that is shifted and distorted. Specifically, when viewed from the sides of a cylindrical glass tumbler, the water and glass act as a magnifying lens, causing the lemon to appear bigger than its actual size. This phenomenon is a common day-to-day experience of optical refraction.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 9: Light – Reflection and Refraction > What you have learnt > p. 158