Reflection of Waves

Introduction

• Waves can be reflected off a boundary.
• Key topics:
  • Drawing ray diagrams.
  • Types of reflection: specular and diffuse.

Behavior of Waves at Boundaries

• When a wave arrives at a boundary between two materials, three outcomes are possible:
  1. Absorption: Wave energy is transferred to the material's energy stores.
  2. Transmission: Wave enters the material, continues traveling, and often refracts.
  3. Reflection: Wave bounces off the surface and does not enter the material.
• The outcome depends on the wave's wavelength and the properties of the two materials.

Ray Diagrams

• Used to show reflection.
• Fundamental rule: Angle of incidence = Angle of reflection.

Steps to Draw a Ray Diagram

1. Start with a boundary between two materials (e.g., air and mirror).
2. Draw the incoming ray of light with an arrow indicating direction.
3. Introduce the normal line:
   • A dashed line perpendicular (90 degrees) to the surface.
4. Measure the angle of incidence:
   • The angle between the incoming ray and the normal.
   • Example: 45 degrees.
5. Draw the reflected ray:
   • Angle of reflection = Angle of incidence.
6. Point of incidence:
   • Where the incoming ray touches the boundary.

Types of Reflection

Specular Reflection

• Occurs on smooth surfaces like mirrors.
• Normals are in the same direction.
• Incoming light rays are reflected in the same direction.
• Produces a clear image, like in a mirror.

Diffuse (Scattered) Reflection

• Occurs on rough surfaces like paper.
• Surface is bumpy; normals point in different directions.
• Incoming rays reflected in various directions.
• No clear image produced; cannot see reflection in paper.
• Despite roughness, the angle of incidence = angle of reflection, but rays scatter due to varying normal directions.

Conclusion

• Understanding reflection helps in various applications.
• Importance of teaching and sharing knowledge on wave reflection.