Light — Class 8 Science NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 8 Science chapter "Light" — 8 important questions with detailed answers for CBSE board exam preparation.

TL;DR: Free step-by-step NCERT solutions for Class 8 Science chapter "Light" — 8 important questions with detailed answers for CBSE board exam preparation.

By Syllab.in · Updated Jun 14, 2026

Key Questions Covered:

Define refraction of light. When does it occur?
A ray of light enters glass from air at 30° to the normal. The refracted ray …
What is dispersion of light? Explain with the example of a prism.
What is a lens? Name two types of lenses.
Why does a pencil in water appear to bend?
What is the power of a lens? Give the formula and its unit.
+ 2 more questions in the full chapter

Solutions Summary:

Question	Status
Define refraction of light. When does it occur?	✓ Solved
A ray of light enters glass from air at 30° to the normal…	✓ Solved
What is dispersion of light? Explain with the example of …	✓ Solved
What is a lens? Name two types of lenses.	✓ Solved
Why does a pencil in water appear to bend?	✓ Solved
What is the power of a lens? Give the formula and its unit.	✓ Solved

Showing 6 of 8 questions

Q1: Define refraction of light. When does it occur?

Refraction is the bending of light when it passes from one transparent medium to another of different optical density. It occurs because light travels at different speeds in different media. Light bends toward the normal when entering a denser medium (water) and away from the normal when entering a rarer medium (air). The angle and amount of bending depend on the refractive indices.

Q2: A ray of light enters glass from air at 30° to the normal. The refracted ray bends by 10°. Find the angle of refraction.

Step 1: Angle of incidence (i) = 30° Step 2: Light bends toward the normal when entering denser medium Step 3: Angle of refraction (r) = 30° - 10° = 20° Angle of refraction = 20°

Q3: What is dispersion of light? Explain with the example of a prism.

Dispersion is the splitting of white light into its component colours when passing through a prism. White light comprises seven colours (VIBGYOR). Different colours have different refractive indices in glass. Red (longer wavelength) bends least, violet (shorter wavelength) bends most. Prism separates these colours spatially, creating a spectrum. Newton proved white light is composite.

Q4: What is a lens? Name two types of lenses.

A lens is a transparent optical device made of glass or plastic with curved surfaces that refract light to form images. Two types: (1) Convex lens (converging)—thicker at center, converges light rays, forms real/virtual images depending on object distance, used in magnifying glasses and cameras. (2) Concave lens (diverging)—thinner at center, diverges light rays, forms virtual images, used in correction of myopia.

Q5: Why does a pencil in water appear to bend?

The pencil appears bent due to refraction of light. Light rays from the submerged part of the pencil refract (bend away from normal) when crossing the water-air boundary. This refraction changes the direction of light rays, making the underwater portion appear displaced and bent relative to the portion above water. Our eye perceives the light's path, not the actual position.

Q6: What is the power of a lens? Give the formula and its unit.

Power of a lens is its ability to converge or diverge light. Formula: P = 1/f, where f = focal length in meters. Unit: Dioptre (D). 1 D = 1/meter. Convex lenses have positive power (converging), concave lenses have negative power (diverging). A +2 D lens has focal length 0.5 m. Power increases as focal length decreases.

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