Ray Optics and Optical Instruments
CBSE · Class 12 · Physics
Quick revision notes for Ray Optics and Optical Instruments — CBSE Class 12 Physics. Key concepts, formulas, and definitions for last-minute revision.
Key Topics to Revise
Introduction to Ray Optics
- Light travels at speed c = 3 × 10⁸ m/s in vacuum
- Light travels in straight lines when wavelength is very small compared to obstacle size
- A ray represents the path of light, and a bundle of rays forms a beam
Reflection by Spherical Mirrors
- Laws of reflection: angle of incidence = angle of reflection, incident ray, reflected ray and normal lie in same plane
- For spherical mirrors, normal passes through center of curvature
- Focal length f = R/2 where R is radius of curvature
Refraction and Snell's Law
- Refraction occurs when light passes from one medium to another
- Snell's law: n₁sin i = n₂sin r
- If n₂ > n₁, ray bends toward normal (denser medium)
Total Internal Reflection
- Occurs when light travels from denser to rarer medium
- Critical angle: sin ic = n₂/n₁ = 1/n₁₂
- For angles greater than critical angle, total internal reflection occurs
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Sources & Official References
- NCERT Official — ncert.nic.in
- CBSE Academic — cbseacademic.nic.in
- CBSE Official — cbse.gov.in
- National Education Policy 2020 — education.gov.in
Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
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