Reflection of Waves

Introduction to Wave Reflection

• When waves hit a boundary between two materials, three outcomes are possible:

  1. Absorption: Wave energy is transferred to the material.
  2. Transmission: Wave passes through the material, often resulting in refraction.
  3. Reflection: Wave bounces off the surface, the focus of this discussion.

• The outcome depends on the wave's wavelength and the properties of the materials.

Ray Diagrams for Reflection

• Ray Diagrams: Used to illustrate reflection.
• Basic Rule: Angle of incidence = Angle of reflection.

Steps to Draw Ray Diagrams

1. Identify the Boundary: Surface where two media meet, e.g., air and mirror.
2. Draw Incoming Ray: Arrow showing the direction towards the boundary.
3. Draw the Normal:
   • A dashed line perpendicular (90 degrees) to the boundary.
   • Helps measure the angle of incidence.
4. Measure Angle of Incidence:
   • Angle between the incoming ray and the normal.
   • Use a protractor if necessary.
5. Draw Reflected Ray:
   • Angle of reflection equals the angle of incidence.
   • Reflected ray is drawn at the same angle from the normal.
6. Point of Incidence: The spot where the incoming ray meets the boundary.

Types of Reflection

• Specular Reflection

  • Occurs on smooth surfaces like mirrors.
  • Normals are parallel, reflecting rays uniformly.
  • Produces clear images.

• Diffuse (or Scattered) Reflection

  • Occurs on rough surfaces like paper.
  • Normals point in various directions due to surface irregularities.
  • Reflects light in multiple directions, preventing clear image formation.

Key Points

• In both specular and diffuse reflection, the angle of incidence equals the angle of reflection.
• Rough surfaces cause normals to point differently, leading to scattered reflection.

Conclusion

• Understanding reflection helps in drawing ray diagrams and explaining why certain materials reflect light differently.
• Encouraged to share the knowledge with peers and teachers.