Wave Optics in 10 Minutes: Last-Minute Revision Mind Map
All essential formulas, concepts, and diagrams for quick revision before JEE Main & Advanced.
Why This Quick Revision Works
Wave optics carries 3-4 questions in every JEE paper. This mind map covers everything you need:
- All essential formulas in one place
- Quick recall techniques for exam pressure
- Common mistakes to avoid
- Diagram-based questions preparation
Huygens Principle & Wavefront
🎯 Key Points:
- Every point on wavefront acts as secondary wavelet source
- New wavefront is envelope of secondary wavelets
- Explains reflection, refraction, and diffraction
📐 Essential Formulas:
Law of Reflection: $\angle i = \angle r$
Snell's Law: $\frac{\sin i}{\sin r} = \frac{n_2}{n_1} = \frac{v_1}{v_2}$
Wave Speed: $v = \frac{c}{n}$
💡 Quick Tip:
Remember: Wavefronts are perpendicular to rays. Closer wavefronts = higher intensity.
Interference & Young's Experiment
🎯 Key Points:
- Superposition of waves from coherent sources
- Constructive: path difference = nλ
- Destructive: path difference = (n+½)λ
- Fringe width β = λD/d
📐 Essential Formulas:
Path Difference: $\Delta x = \frac{yd}{D}$
Fringe Width: $\beta = \frac{\lambda D}{d}$
Condition for Maxima: $\Delta x = n\lambda$
Condition for Minima: $\Delta x = (n+\frac{1}{2})\lambda$
Angular Width: $\theta = \frac{\lambda}{d}$
💡 Quick Tip:
If white light used: central fringe white, colored fringes with violet inner, red outer.
Diffraction & Polarization
🎯 Key Points:
- Single slit: central maximum twice as wide
- Diffraction grating: multiple slits for sharper pattern
- Polarization: transverse wave phenomenon
- Brewster's law: reflected light completely polarized
📐 Essential Formulas:
Single Slit Minima: $a\sin\theta = n\lambda$
Grating Equation: $d\sin\theta = n\lambda$
Brewster's Law: $\tan i_p = \frac{n_2}{n_1}$
Malus Law: $I = I_0\cos^2\theta$
Resolving Power: $R = \frac{\lambda}{\Delta\lambda} = nN$
💡 Quick Tip:
Diffraction ≠ refraction! Diffraction occurs at edges, refraction at interface.
🧠 Wave Optics Mind Map
Interference
- • Young's Double Slit
- • Coherent Sources Required
- • Fringe Pattern
- • Intensity Variation
- • White Light Effects
Diffraction
- • Single Slit Pattern
- • Diffraction Grating
- • Resolving Power
- • X-ray Diffraction
Polarization
- • Malus Law
- • Brewster's Angle
- • Polaroids
- • Applications
Wave Theory
- • Huygens Principle
- • Wavefronts & Rays
- • Reflection/Refraction
- • Doppler Effect
🚀 Exam Success Strategies
Formula Recall:
- Fringe width β ∝ λ, ∝ D, ∝ 1/d
- Resolving power increases with N (slits)
- Brewster angle depends on refractive indices
- Malus law: intensity ∝ cos²θ
Common Mistakes:
- Confusing interference & diffraction
- Wrong sign in path difference
- Forgetting central maxima width in diffraction
- Missing polarization in MCQ options
Advanced Applications Available
Includes Doppler effect in light, resolving power problems, and JEE Advanced level applications
📝 2-Minute Revision Test
Quick questions to test your recall:
1. Fringe width in YDSE when screen distance doubled?
2. Condition for first minima in single slit diffraction?
3. Brewster angle for air-glass interface (n=1.5)?
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