JEE Main Optics: Ray Optics and Wave Optics Complete Study Guide
Optics is a 3-question block in JEE Main Physics that combines conceptual understanding with formula application. Ray Optics is more calculation-heavy while Wave Optics tests physical intuition.
Ray Optics: Mirrors and Lenses
Mirror formula: 1/v + 1/u = 1/f. Lens formula: same with sign conventions. Power of lens P = 1/f (in meters). Combination of lenses: 1/f = 1/f₁ + 1/f₂. Common JEE question: object placed inside focal length of lens — find image position and nature.
Prisms and Refraction
Snell's law: n₁sinθ₁ = n₂sinθ₂. Critical angle: sinC = 1/n. Total internal reflection conditions. Prism: δ = (n-1)A for small angle, minimum deviation for equilateral prism (standard formula). Dispersion by prism.
Optical Instruments (1 question)
Simple microscope (M = 1 + D/f), compound microscope, telescope (refracting and reflecting). JEE Main: Given f_objective and f_eyepiece, find magnification and tube length.
Wave Optics: Young's Double Slit
Fringe width β = λD/d. Condition for constructive: path difference = nλ. Condition for destructive: (2n-1)λ/2. Effect of changing medium (λ changes), moving slits, or using white light. Intensity: I = 4I₀cos²(δ/2).
Diffraction and Polarization
Single slit diffraction: first minimum at sinθ = λ/a. Brewster's law: n = tan(i_p). Malus's law: I = I₀cos²θ. JEE Main commonly tests polarization through two polaroids as Malus's law calculation.
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