Ch 10 covers reflection (plane and spherical mirrors) and refraction (glass, lenses). Students learn sign convention, mirror formula, lens formula, magnification, and power of a lens.
Laws of reflection: angle of incidence = angle of reflection; incident ray, reflected ray, and normal lie in the same plane. Spherical mirrors: concave (converging — used in torches, headlights, dentist mirrors) and convex (diverging — used in rear-view mirrors). Mirror formula: 1/v + 1/u = 1/f (new cartesian sign convention). Magnification m = h′/h = −v/u.
Refraction: bending of light when passing between media of different densities. Snell's law: n₁ sin i = n₂ sin r. Refractive index n = speed in vacuum / speed in medium. Convex lens: converging (reading glasses, magnifier). Concave lens: diverging (correcting myopia). Lens formula: 1/v − 1/u = 1/f. Power P = 1/f (in metres), unit: dioptre (D).
Download: https://ncert.nic.in/textbook/pdf/jesc110.pdf | Complete book: https://ncert.nic.in/textbook/pdf/jesc1ps.zip
When light travels from water (denser) to air (rarer), it bends away from the normal (refraction). The bottom of the pool appears to be raised — this is called apparent depth. The apparent depth is less than the real depth because of this bending of light.
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