Optics
Reflection, refraction, lenses, wave optics, diffraction
Key Concepts
- Reflection: angle of incidence = angle of reflection
- Snell's law: n₁ sinθ₁ = n₂ sinθ₂; TIR occurs when θ > critical angle
- Lens formula and mirror formula use same sign convention
- Young's double slit: interference pattern with bright and dark fringes
- Diffraction: bending of waves around obstacles; single slit produces central maximum
Important Formulae
| Mirror/lens formula | 1/f = 1/v − 1/u |
| Magnification (mirror) | m = −v/u |
| Snell's law | n₁ sinθ₁ = n₂ sinθ₂ |
| Critical angle | sin C = 1/n (n = refractive index) |
| Fringe width (YDSE) | β = λD/d |
| Lens maker's formula | 1/f = (n−1)(1/R₁ − 1/R₂) |
Quick Tips
- New Cartesian sign convention: distances measured from pole; along incident ray = positive.
- Power of lens P = 1/f (in metres); unit = dioptre. Lenses in contact: P = P₁ + P₂.
- In YDSE: path difference = nλ for bright fringe; (2n−1)λ/2 for dark fringe.
Sample Practice Questions
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The phenomenon of light travelling in a straight line is explained by:
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Answer: Rectilinear propagation
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Resolving power of a microscope is defined as the minimum separation:
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Answer: That can be seen as distinct
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The condition for constructive interference in YDSE:
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Answer: Path difference = nλ
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Critical angle and total internal reflection occurs when light goes from:
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Answer: Denser to rarer medium
Practice Questions
Practice 20 randomly selected NEET questions on Optics. Answers are revealed after each question.
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What are the key concepts in Optics for NEET?
Reflection: angle of incidence = angle of reflection; Snell's law: n₁ sinθ₁ = n₂ sinθ₂; TIR occurs when θ > critical angle; Lens formula and mirror formula use same sign convention; Young's double slit: interference pattern with bright and dark fringes; Diffraction: bending of waves around obstacles; single slit produces central maximum.
Which formulae are important for Optics in NEET?
Mirror/lens formula: 1/f = 1/v − 1/u; Magnification (mirror): m = −v/u; Snell's law: n₁ sinθ₁ = n₂ sinθ₂; Critical angle: sin C = 1/n (n = refractive index); Fringe width (YDSE): β = λD/d; Lens maker's formula: 1/f = (n−1)(1/R₁ − 1/R₂).
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