Lecture Notes: Physics - Ray Optics and Optical Instruments

Jai Shri Ram

• Welcome everyone.
• Important chapter for Class 12th board: Ray Optics and Optical Instruments.

Board Exam Preparation

• Important for all boards.
• Full chapter discussion.
• PDF, printed notes, t gra channel: major updates, session notes, mind maps.

Topics Covered

• **Reflection
• Refraction
• Lenses
• Prisms
• Deviation
• Dispersion
• Optical Instruments

Laws of Reflection

• Meaning of Reflection: When light ray bounces back into the same medium.
• Rules:
  • Angle of Incidence (i) = Angle of Reflection (r)
  • Incident Ray, Reflected Ray, and Normal lie in the same plane.

Images

• Real vs Virtual Images:
  • Real Image: Can be obtained on a screen.
  • Virtual Image: Appears inside a mirror.

Spherical Mirrors

• Types: Concave, Convex.
• Terminology: Pole, Center of Curvature, Radius of Curvature, Principal Axis, Focal Point.
• Mirror Formula:
  • 1/f = 1/v + 1/u

Image Formation by Spherical Mirrors

• Concave Mirror: Real, inverted images in most cases.
• Convex Mirror: Virtual, erect images.

Sign Convention

• Positive & Negative distances: Radial distances are positive if measured against the direction of incident light.

Magnification

• Lateral Magnification: m = height of image (hi) / height of object (ho)
• Formula: m = -v / u

Refraction and Refractive Index

• Refraction: The bending of light when it passes from one medium to another.
• Refractive Index: Ratio of speed of light in vacuum (c) to its speed in medium (v): n = c/v.
• Snell's Law: n = sin(i) / sin(r)

Real and Apparent Depth

• Apparent Depth = Real Depth / Refractive Index.

Total Internal Reflection (TIR)

• Conditions:
  • Light passes from denser to rarer medium.
  • Angle of Incidence > Critical Angle.

Applications of TIR

• Mirage Creation.
• Optical Fibers: Light signals travel with minimal loss.

Prisms

• Angle of Prism (A).
• Deviation Angle (δ): δ = (i + e - A)

Dispersion of Light

• Chromatic Dispersion: Separation of white light into its spectral colors.

Lenses

• Types: Convex (Converging), Concave (Diverging).
• Lens Formula: 1/f = 1/v - 1/u
• Magnification: m = hi/ho = v/u
• Power of Lens: P = 1/f (in meters).

Combination of Lenses

• Effective Power: P = P1 + P2

Optical Instruments

• Microscope: Simple, Compound.
• Telescopes: Astronomical, Terrestrial.
• Key Metrics: Magnification, Resolving Power.

Summary

• Completes all main points of Ray Optics and Optical Instruments.
• Practice problems session follows next.
• Mind-Mapping for revision.

Channels for Further Study

• PDFs, Session Updates on the provided channel links.