Light – Reflection and Refraction Class 10: Formulas, Ray Diagrams & NCERT Solutions
Master Class 10 Physics Light Reflection and Refraction: Mirror formula, Lens formula, Snell's law, sign conventions, solved numericals, and board questions.
Light – Reflection and Refraction Study Guide
Light is a form of electromagnetic radiation that travels in straight lines in vacuum at a speed of c ≈ 3 × 10⁸ m/s and gives us visual perception of our surroundings.
Laws of Reflection
- The angle of incidence equals the angle of reflection: ∠i = ∠r
- The incident ray, reflected ray, and the normal to the surface at the point of incidence all lie in the same geometric plane.
Mirror Formula & Sign Convention
1/v + 1/u = 1/fLinear Magnification (m):
m = h' / h = -v / u
New Cartesian Sign Convention: The object distance (u) is always negative. Concave mirrors have real focus (f < 0); Convex mirrors have virtual focus (f > 0).
Refraction of Light & Snell's Law
Refraction occurs because light travels with different speeds in different optical media. According to Snell's Law of Refraction:
sin i / sin r = n₂₁ = n₂ / n₁ = v₁ / v₂Absolute Refractive Index:
n = c / v (where c is speed in vacuum, v is speed in medium).
Lenses & Lens Formula
1/v - 1/u = 1/fLens Magnification:
m = h'/h = +v/uPower of Lens (P):
P = 1 / f (in metres). SI Unit: Dioptre (D).
Indexed Topics & Examination Keywords
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