Chapter 20 · Class 11-12 & JEE/NEET

Ray Optics

57 topics in 13 parts

Full lessonClass 12 Physics · Ray Optics Practice295 practice questions

Key formulas

Snell's Law of Refraction
$n_1 \sin i = n_2 \sin r, \quad \sin\theta_c = \frac{n_2}{n_1} \quad (n_1 > n_2)$
Mirror Formula & Magnification
$\frac{1}{v} + \frac{1}{u} = \frac{1}{f}, \quad m = -\frac{v}{u} = \frac{f - v}{f} = \frac{f}{f - u}$
Lensmaker's Equation
$\frac{1}{f} = (n_{rel} - 1)\left( \frac{1}{R_1} - \frac{1}{R_2} \right), \quad \frac{1}{v} - \frac{1}{u} = \frac{1}{f}$
Prism Deviation & Refractive Index
$A + \delta = i + e, \quad \mu = \frac{\sin\left(\frac{A + \delta_m}{2}\right)}{\sin\left(\frac{A}{2}\right)}$

Mirror formula Lens formula Snell's law Lens maker's formula Law of reflection Spherical mirror focal length

Key ideas

Refraction Through a Glass Prism: Angle of Deviation & Minimum Deviation Condition

4. Systematic Comparison & Parameter Classifications

Object Position	Image Position	Size of Image	Nature of Image
At Infinity	At Focus (F)	Highly Diminished (Point)	Real and Inverted
Beyond Center of Curvature (C)	Between C and F	Diminished	Real and Inverted
At Center of Curvature (C)	At C	Same Size	Real and Inverted
Between C and Focus (F)	Beyond C	Magnified (Enlarged)	Real and Inverted
Between Focus (F) and Pole (P)	Behind the Mirror	Enlarged	VIRTUAL and ERECT

Exam Worked Example

Problem: A ray of light passes through an equilateral prism (A = 60°) with refractive index μ = √3. Calculate the angle of minimum deviation δ_m and the angle of incidence i.

● Step 1: Formula for minimum deviation: μ = sin[(A + δ_m)/2] / sin(A/2).

● Step 2: Here A = 60°, sin(A/2) = sin(30°) = 0.5. So sin[(60° + δ_m)/2] = √3 * 0.5 = √3/2.

● Step 3: (60° + δ_m) / 2 = 60° → 60° + δ_m = 120° → Minimum deviation δ_m = 60°.

● Step 4: Angle of incidence at minimum deviation: i = (A + δ_m) / 2 = (60° + 60°) / 2 = 60°.

Checkpoint

1. When a biconvex glass lens of refractive index 1.5 is immersed in a liquid of refractive index 1.7, how does it behave?

All 57 topics in Ray Optics

Reflection of Light & Plane Mirrors
- Laws of Reflection
- Diffused & Regular Reflection
- Image Formation by Plane Mirror
- Multiple Plane Mirrors & Image Count
- Field of View & Extended Object Image
- Motion of Object & Image in Plane Mirror
- Vector Representation of a Light Ray
Spherical Mirrors
- Sign Convention & Ray Diagram Rules
- Mirror Formula & Focal Length
- Image Formation by Concave & Convex Mirrors
- Transverse & Longitudinal Magnification
- Velocity of Object & Image in Curved Mirror
Refraction of Light at Plane Surfaces
- Laws of Refraction & Snell's Law
- Deviation of a Light Ray
- Variable Refractive Index Medium
- Speed & Wavelength Change in Refraction
- Atmospheric Refraction
Total Internal Reflection & Critical Angle
- Critical Angle & Conditions of TIR
- Graph of Angle of Deviation vs. Incidence
- Optical Fibres & Applications
Refraction Through Slabs & Apparent Shift
- Apparent Depth & Apparent Shift
- Lateral Displacement Through a Parallel Slab
- Refraction Across Multiple Slabs
- Combination of Glass Slab & Mirror
- Refractive Index Measurement by Travelling Microscope
Refraction at Spherical Surfaces
- Single Spherical Refracting Surface
- Formula for Refraction at a Curved Surface
- Lateral Magnification for a Spherical Surface
Thin Lens
- Lensmaker's Formula
- Formula & Image Formation
- Magnification
- Power of a Lens
- Cut & Split Lenses
- Lenses With Different Media on Either Side
Lens Experiments & Focal Length Methods
- Lens Displacement Method
- Graphical Method for Focal Length of a Convex Lens
- Measurement of Refractive Index of a Liquid by a Convex Lens
Silvered Lenses & Lens-Mirror Combinations
- Lenses Placed in Contact & at a Distance
- Equivalent Mirror of a Silvered Lens
- Lens & Mirror Combinations
- Image Formed at the Object Itself
Prism & Ray Deviation
- Refraction Through a Prism & Deviation Angle
- Condition of Minimum Deviation
- Condition of Grazing Emergence & No Emergence
- Condition of Maximum Deviation
- Thin & Submerged Prisms
Dispersion of Light
- Angular Dispersion & Dispersive Power
- Deviation Without Dispersion
- Dispersion Without Deviation
- Rainbow & Light Scattering
Optical Instruments
- Simple Microscope & Magnifying Glass
- Compound Microscope
- Astronomical & Terrestrial Telescopes
- Lens Camera
Defects of Vision & Optical Aberrations
- Human Eye & Defects of Vision
- Myopia & Hypermetropia Correction
- Chromatic & Spherical Aberration