Human Eye and Colourful World — Telangana (SSC) Class 10 Science Solutions (Free)

Human eye main parts: 1. Cornea: Transparent front layer, refracts light 2. Lens: Biconvex, adjustable focal length for accommodation 3. Retina: Light-sensitive layer at back, contains rods and cones, converts light to nerve signals Other parts: Iris (controls pupil), ciliary muscles (adjust lens), optic nerve (sends signals to brain)

Accommodation: Ability of eye to focus on objects at different distances. Mechanism: Ciliary muscles contract to change the shape of lens. For near objects: Ciliary muscles contract → lens becomes thicker → focal length decreases → image focuses on retina For distant objects: Ciliary muscles relax → lens becomes thinner → focal length increases → image focuses on retina

Myopia (short-sightedness): Far objects appear blurred, near objects clear. Cause: Eyeball too long OR cornea too curved → images form in front of retina Correction: Concave lens (diverging) placed in front of eye. Concave lens diverges rays before entering eye, shifting focus point back to retina. Prescription uses negative power (e.g., -2.5 D)

Hypermetropia (long-sightedness): Near objects appear blurred, far objects clear. Cause: Eyeball too short OR cornea too flat → images form behind retina Correction: Convex lens (converging) placed in front of eye. Convex lens converges rays before entering eye, shifting focus point forward to retina. Prescription uses positive power (e.g., +2.5 D)

Dispersion: Splitting of white light into constituent colors (spectrum) due to different refractive indices for different wavelengths. Caused by: Prism or water droplets (rainbows) Seven colors in order (VIBGYOR): Violet, Indigo, Blue, Green, Yellow, Orange, Red Violet has smallest wavelength (bends most), Red has largest wavelength (bends least)