Lecture on Reflection and Lenses

Introduction

• Review of electromagnetic spectrum with focus on visible light.
• Introduction to the concept of reflection and formation of images.

Reflection

• Definition: Bouncing of light rays when they hit a surface.
• Types of Reflection:
  • Specular Reflection:
    • Occurs on smooth surfaces like plain mirrors.
    • Angle of incidence equals angle of reflection.
  • Diffuse Reflection:
    • Occurs on rough surfaces like rocks and buildings.
    • Light is scattered in many directions.

Law of Reflection

• The angle of incidence is equal to the angle of reflection.
• Angle measurements:
  • Incident ray to normal line.
  • Reflected ray to normal line.

Image Characteristics

• Definitions:
  • Real vs Virtual Images: Real images form when rays converge; virtual when rays appear to diverge.
  • Orientation: Upright or inverted.
  • Location: Depends on object's location.
  • Size and Magnification: Comparison and ratio of image size to object size.

Plane Mirrors

• Produce virtual, upright, laterally inverted images.
• Magnification is 1.
• Lateral Inversion: Left and right sides are reversed.
  • Example: "AMBULANCE" on vehicles.

Curved Mirrors

• Types:
  • Concave Mirrors: Reflecting surface inside sphere.
    • Terms:
      • Principal Axis, Center of Curvature (C), Vertex (A), Focal Point (F).
    • Image characteristics vary with object location.
      • Beyond C: Inverted, smaller, real image.
      • At C: Inverted, same size, real image.
      • Between C and F: Inverted, larger, real image.
      • At F: No image.
      • Beyond F: Upright, larger, virtual image.
  • Convex Mirrors: Reflecting surface outside sphere.
    • Always produce virtual, upright, smaller images.

Mirror Equation

• Formula: 1/F = 1/P + 1/Q
• Magnification: h'/h = -Q/P
• Sign conventions for mirror:
  • F is positive for concave, negative for convex.
  • Image distance positive for real, negative for virtual.
  • Image height positive for upright, negative for inverted.

Solving Mirror Problems

• Example provided with calculation steps for image distance and size.

Lenses

• Types:
  • Convex (Converging) Lenses: Thick in the middle, thin at edges.
  • Concave (Diverging) Lenses: Thin in the middle, thick at edges.

Lens Characteristics

• Convex Lenses:
  • Image characteristics vary with object location.
    • Beyond 2F: Smaller, inverted, real.
    • At 2F: Same size, inverted, real.
    • Between 2F and F: Larger, inverted, real.
    • At F: No image.
    • Inside F: Larger, upright, virtual.
• Concave Lenses:
  • Always produce smaller, upright, virtual images.

Lens Equation

• Similar to mirror equation.
• Sign conventions for lenses differ slightly.
  • F is positive for double convex, negative for double concave.
  • Image distance positive for real, negative for virtual.
  • Image height positive for upright, negative for inverted.

Summary

• Reflection laws and image characteristics.
• Differences in image formation between mirrors and lenses.

Outro

• Promoted next video about the use of mirrors and lenses in optical devices.