Lecture Notes on Refraction of Light

Key Concepts

• Rectilinear Propagation of Light: Light travels in a straight line.
• Refraction of Light: Bending of light as it travels from one medium to another.

Magic Trick Demonstration

• Materials Needed: Transparent glass filled with water.
• Activity: Hold the glass in front of the screen to observe changes in the direction of an arrow due to refraction.

Basic Principles of Light

• Beam of Light: Composed of many rays traveling straight.
• Single Ray of Light: Can be bent using a transparent material such as glass or plastic.

Definition of Refraction

• Refraction is defined as the change in direction of light when it travels obliquely from one medium to another.
  • Incident Ray: The ray of light that hits the second medium.
  • Point of Incidence: The point where the incident ray hits the second medium.
  • Normal: An imaginary line perpendicular to the boundary between two materials.
  • Refracted Ray: The ray of light that is bent as it enters the second medium.
  • Angle of Incidence: Angle between the incident ray and the normal.
  • Angle of Refraction: Angle between the refracted ray and the normal.

Examples of Refraction

• Pencil in Water: Pencil appears bent when submerged in a glass of water.
• Swimming Pool: Water appears shallower than it really is due to refraction.

Why Refraction Happens

• Change in Speed of Light:
  • Speed of light in air: ~3 x 10^8 m/s.
  • Speed of light in glass: ~2 x 10^8 m/s.
  • Refraction occurs due to the change in speed as light enters different mediums.

Types of Refraction

1. From Rarer to Denser Medium:
   • Light bends towards the normal.
   • Angle of incidence > Angle of refraction.
2. From Denser to Rarer Medium:
   • Light bends away from the normal.
   • Angle of incidence < Angle of refraction.
3. Normal Incidence:
   • Light travels along the normal line; no bending occurs even though speed changes.
   • Angle of incidence = Angle of refraction = 0.

Conclusion

• Refraction is the bending of light due to changes in speed as it moves between different optical materials.

Top Three Questions

• Questions related to refraction will be provided for practice.
• Encourage interaction in the comments for further clarification and discussion.