A lemon kept in water in a glass tumbler appears to be larger than its actual size. It is because of
- (a)reflection of light
- (b)scattering of light
- (c)refraction of light
- (d)polarization of light
Correct — C, refraction of light. When light passes from water (and the glass) into air it bends, because the media have different optical densities; this bending, called refraction, makes the submerged lemon appear larger and shifted from its true position. The curved tumbler of water effectively acts like a magnifying lens.
- (a)reflection of light — Reflection is the bouncing back of light from a surface, as in a mirror; it does not enlarge an object seen through water.
- (b)scattering of light — Scattering is the redirection of light by small particles (why the sky is blue); it does not magnify a submerged object.
- (d)polarization of light — Polarisation restricts the vibration direction of light waves (used in Polaroid filters); it has nothing to do with apparent size.
Refraction is the change in direction of light as it crosses the boundary between media of different refractive index. Because water and glass are optically denser than air, light rays from the lemon bend as they leave, and the eye traces them back to a larger, displaced virtual image.
The clue is 'appears larger' when seen through water — that is magnification produced by bending of light (refraction), not by bouncing (reflection) or by particles (scattering).
- Refraction is the bending of light when it moves between media of different refractive index.
- Water and glass are optically denser than air, so light bends on leaving them.
- A curved water surface can act like a converging lens, magnifying the object.
- Refraction also explains a bent-looking pencil in water and the apparent shallowness of a pool.
- Choosing reflection because a glass surface also reflects some light.
- Confusing refraction with scattering, which explains colour rather than size.
Everyday optics is asked as 'why does X appear bent/larger/shifted' — apparent size or bending through water points to refraction.
Sun's halo is produced by the refraction of light in
- (a) Water vapour, in Stratus clouds
- (b) Ice crystals in Cirrocumulus clouds
- (c) Ice crystals in Cirrus clouds
- (d) Dust particles in Stratus clouds
Answer(c) Ice crystals in Cirrus clouds
Same phenomenon — refraction (bending) of light. The UPSC item applies refraction to the Sun's halo through ice crystals; this one applies it to the apparent magnification of a lemon in water.
- practice — not a real PYQ
A pencil partly dipped in a glass of water appears bent at the surface. This is due to
- (a)reflection
- (b)refraction
- (c)dispersion
- (d)diffraction
Answer(b) refraction — light bends as it crosses the water–air boundary.
- practice — not a real PYQ
A swimming pool appears shallower than its real depth because of
- (a)reflection of light
- (b)refraction of light
- (c)scattering of light
- (d)total internal reflection
Answer(b) refraction of light — the apparent-depth effect.