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Cheat sheet · NEET Preparation Physics

Wave Optics cheat sheet

The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.

NEET · Physics

Cheat sheet

Class 12 · Chapter 10Wave Optics

YDSE fringe width β = λD/d.

1. Huygens' Principle

Every point on a wavefront is a source of secondary wavelets; the new wavefront is their envelope. Explains reflection and refraction.

2. Interference (YDSE)

β=λDd\beta = \dfrac{\lambda D}{d}
Δx=nλ\Delta x = n\lambda (bright)Δx=(2n−1)λ2\Delta x = (2n - 1)\dfrac\lambda2 (dark)

Needs coherent sources.

3. Diffraction

asin⁡θ=nλa\sin\theta = n\lambda (minima)
Width of central max=2λDa\text{Width of central max} = \dfrac{2\lambda D}{a}

4. Polarisation

I=I0cos⁡2θI = I_0\cos^2\theta (Malus)tan⁡iB=μ\tan i_B = \mu (Brewster)

Only transverse waves can be polarised.

5. Key Points

  • Fringe width ∝ λ.
  • In water, fringes become narrower (λ/μ).
  • Resolving power improves with larger aperture.
  • Polaroids: sunglasses, 3-D films.

Remember: Huygens | β = λD/d | single slit | Malus & Brewster

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