NCERT Solutions for Class 10 Science Chapter 10 The Human Eye and the Colourful World

Short Note:

• Power of Accommodation: The ability of the eye lens to adjust its focal length using ciliary muscles to focus both near and distant objects clearly on the retina.

• Near Point & Far Point: The minimum distance for clear vision is 25 cm (Near Point). The maximum distance is Infinity (Far Point).

• Myopia (Near-sightedness): Person can see nearby objects clearly but cannot see distant objects. Corrected using a Concave lens.

• Hypermetropia (Far-sightedness): Person can see distant objects clearly but cannot see nearby objects. Corrected using a Convex lens.

• Presbyopia: Age-related reduction in power of accommodation due to weakening ciliary muscles. Corrected using Bifocal lenses.

Short Note:

When light passes through a triangular glass prism, it undergoes refraction twice—at the entering surface and at the exiting surface. Due to the inclined refracting faces of the prism, the emergent ray bends at an angle to the direction of the incident ray. This angle is called the Angle of Deviation (δ).

Short Note:

• Dispersion: The splitting of white light into its component seven colors (VIBGYOR) when passing through a transparent medium like a prism.

• Cause: Different wavelengths bend by different angles relative to the incident ray. Red light bends the least, while Violet light bends the most.

• Rainbow Formation: Formed by dispersion, refraction, and internal reflection of sunlight by tiny water droplets suspended in the atmosphere after rain.

Short Note:

Atmospheric refraction occurs due to continuous variation in air density and refractive index in different layers of Earth's atmosphere.

• Twinkling of Stars: Continuous fluctuations in atmospheric refractive index alter the apparent position and brightness of starlight.

• Advanced Sunrise & Delayed Sunset: The sun is visible to us about 2 minutes before actual sunrise and 2 minutes after actual sunset due to atmospheric bending of light.

Short Note:

• Tyndall Effect: Scattering of a beam of light by colloidal particles in a fine suspension, making the path of light visible (e.g., sunlight entering a dusty canopy).

• Blue Sky: Fine air molecules scatter light of shorter wavelengths (blue end) more strongly than longer wavelengths (red end).

• Red Sunrise/Sunset: At sunrise and sunset, light travels longer atmospheric paths. Shorter blue wavelengths scatter away, while longer red wavelengths reach our eyes.