Ray & Wave Optics
Practice JEE Main Ray & Wave Optics chapter-wise PYQs online. Lens maker’s formula, Young’s double slit experiment (YDSE), Brewster’s angle & solutions.
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🎯 High-Yield Syllabus Breakdown
These high-frequency concepts account for over 90% of all questions asked in Ray & Wave Optics:
- Reflection & Mirror Formula 1/f = 1/v + 1/u, Magnification m = -v/u
- Refraction, Critical Angle sin θ_c = 1/μ, Total Internal Reflection (TIR)
- Lens Maker’s Formula 1/f = (μ_L/μ_M - 1)(1/R₁ - 1/R₂) & Optical Power P = 1/f
- Prism Formula μ = sin[(A + D_m)/2] / sin(A/2)
- Young’s Double Slit Experiment: Fringe Width β = λ D / d
- Diffraction at Single Slit (a sin θ = nλ) & Polarization (Brewster’s Law tan i_B = μ)
⚡ Essential Formulas & Speed Shortcuts
Formulas and time-saving shortcuts to solve Optics questions in under 45 seconds:
Glass lens in water: Focal length quadruples: f_water = 4 · f_air for glass (μ=1.5) in water (μ=4/3).
YDSE Fringe Width: β = λ D / d.
Brewster’s Angle: tan i_p = μ; reflected and refracted rays are perpendicular (90°).
📖 Sample Solved Exam Questions
Preview authentic questions from this chapter with full step-by-step solutions:
💡 View Step-by-Step Solution & Answer
Correct Answer: 80 cm
- Step 1: Lens maker's formula in medium: 1/f = (μ_lens / μ_med - 1) (1/R₁ - 1/R₂).
- Step 2: In air (μ_med = 1): 1/f_air = (1.5 - 1) K = 0.5 K => K = 2 / 20 = 1/10.
- Step 3: In water (μ_med = 4/3): 1/f_water = [(1.5 / (4/3)) - 1] K = [(3/2 × 3/4) - 1] K = (9/8 - 1) K = (1/8) K.
- Step 4: Substitute K = 1/10: 1/f_water = (1/8) × (1/10) = 1/80 => f_water = 80 cm.
⚡ Speed Tip: Standard glass lens in water ratio: f_water = 4 × f_air = 4 × 20 = 80 cm.
💡 View Step-by-Step Solution & Answer
Correct Answer: 1.0 mm
- Step 1: Formula for fringe width in YDSE is β = λ D / d.
- Step 2: Convert all quantities to SI units: λ = 500 × 10⁻⁹ m, D = 1 m, d = 0.5 × 10⁻³ m.
- Step 3: Substitute into formula: β = (500 × 10⁻⁹ × 1) / (0.5 × 10⁻³).
- Step 4: β = 1000 × 10⁻⁶ m = 10⁻³ m = 1.0 mm.
⚡ Speed Tip: YDSE fringe width: β = λD / d = (500 × 10⁻⁹ × 1) / (0.5 × 10⁻³) = 1 mm.
💡 View Step-by-Step Solution & Answer
Correct Answer: sin⁻¹(2/3)
- Step 1: Condition for total internal reflection: ray travels from denser medium (μ₁) to rarer medium (μ₂).
- Step 2: By Snell's Law at critical angle θ_c: μ₁ sin θ_c = μ₂ sin 90°.
- Step 3: For glass to air: 1.5 sin θ_c = 1 × 1 => sin θ_c = 1 / 1.5 = 1 / (3/2) = 2/3.
- Step 4: Therefore, θ_c = sin⁻¹(2/3) ≈ 41.8°.
⚡ Speed Tip: Critical angle formula: sin θ_c = 1 / μ = 1 / (3/2) = 2/3.
❓ Frequently Asked Questions (FAQs)
What happens to the focal length of a lens when it is immersed in water?
For a glass lens (μ = 1.5) immersed in water (μ = 4/3), its focal length increases by 4 times.