Reflection
Physics · परावर्तन
📋Quick Overview
When light bounces back after hitting a surface, it is called reflection. A mirror reflects light. There are two laws of reflection: (1) Angle of incidence = Angle of reflection, (2) The incident ray, reflected ray, and normal all lie in the same plane. Light travels in straight lines at 3 × 10⁸ m/s (fastest speed in the universe).
📖Plane Mirror — Image Properties
- •Image is VIRTUAL (cannot be caught on screen) and ERECT (upright)
- •Image is SAME SIZE as object
- •Image is at SAME DISTANCE behind mirror as object is in front
- •Image is LATERALLY INVERTED (left becomes right, right becomes left) — that's why 'AMBULANCE' is written in reverse on ambulances!
- •If two plane mirrors are at angle θ, number of images = (360/θ) - 1
- •Parallel mirrors (θ = 0°) create INFINITE images
📖Concave vs Convex Mirror
📖Mirror Formula & Key Terms
Mirror Formula: 1/f = 1/v + 1/u. Where f = focal length, v = image distance, u = object distance. Magnification: m = -v/u = height of image / height of object. Sign Convention: All distances measured from pole. Distances along incident light = positive, against = negative.
- •Pole (P) = center of the mirror surface
- •Centre of Curvature (C) = center of the sphere of which mirror is a part
- •Radius of Curvature (R) = radius of that sphere
- •Focus (F) = point where parallel rays converge/appear to diverge. f = R/2
- •IMPORTANT: Focal length = half of radius of curvature (f = R/2)