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Class 10 Science Chapter 9 – Revision Notes: Light: Reflection and Refraction
- Focal length & radius of curvature: f = R/2 for spherical mirrors.
- Mirror formula: 1/v + 1/u = 1/f (sign convention: distances measured from the pole, distances against incident light direction are negative).
- Magnification (mirror): m = -v/u = h’/h.
- Lens formula: 1/v – 1/u = 1/f.
- Magnification (lens): m = v/u = h’/h.
- Power of a lens: P = 1/f (f in metres); SI unit dioptre (D). Convex lens: positive power. Concave lens: negative power.
- Lens combination in contact: Pcombined = P1 + P2 + …
- Refractive index: n = speed of light in vacuum / speed of light in medium = c/v.
- Concave mirror images: real & inverted when object is beyond F; virtual, erect & magnified when object is between pole and F.
- Convex mirror images: always virtual, erect, and diminished, regardless of object position.
- Convex lens images: real & inverted when object is beyond F; virtual, erect & magnified when object is between the lens and F.
- Concave lens images: always virtual, erect, and diminished.
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