Lecture Notes: Convex and Concave Lenses

Introduction

• Topic: Convex and concave lenses
• Purpose: To explore how these lenses help us understand the universe

What is a Lens?

• A lens is a transparent object made of glass or plastic with curved sides.
• Lenses can bend light rays as they pass through, changing direction.
• This bending process is called refraction (the change of direction of light rays as they move from one medium to another).

Types of Lenses

1. Convex Lens

   • Two spherical surfaces curved outwards.
   • Thicker in the middle, thinner at the edges.

2. Concave Lens

   • Two spherical surfaces curved inwards.
   • Thinner in the middle, thicker at the edges.

How Lenses Work

• Function through refraction (bending of light rays).
• Refraction occurs in two ways:
  1. Convergence
  2. Divergence

Convex Lens Mechanics

• An incident ray projected on a convex lens at an angle.
• Normal Line: A line drawn from the point of incidence (touching point of the ray and lens).
• Inside the lens:
  • Ray enters, slows down due to the denser medium (glass) and bends towards the normal line.
  • As it exits back into air (less dense), it speeds up and bends away from the normal line.
• Multiple rays converge at a common point known as the focal point.
• The image is projected beyond the focal point.

Concave Lens Mechanics

• Incident rays projected towards a concave lens diverge after refraction.
• Rays extend backward and appear to meet at a point behind the lens.
• A virtual image forms at this focal point.

Additional Concepts

• Focal Length: Distance from the center of the lens to the focal point.
• Focal length and the distance between the lens and the object affect image size.

Conclusion

• Recap of the mechanics of how convex and concave lenses refract light.
• Importance in understanding visual images and projecting them.

Sign-off

• Lecture by Dr. Binox, signing out.