Reflection of (light) Waves

Reflection of (light) Waves

1. Reflection of light lets us see things

   • Visible light is a transverse wave
   • When light reflects off an uneven surface, the light reflects off at all different angles and you get a diffuse reflection
     • When light reflects off an even surface then it's all reflected off at the same angle and you get a clear reflection
   • The law of reflection applies to every reflected ray
     • ANGLE OF INCIDENCE = ANGLE OF REFLECTION
   • Two angles are always defined between the ray and the dotted normal

2. Refractive Index

   • The refractive index of a transparent material tells you how fast light travels in material
   • REFRACTIVE INDEX (N) = SPEED OF LIGHT IN A VACUUM (C) / SPEED OF LIGHT IN THAT MATERIAL (V)
   • According to snell's law, the angle of incidence, angle of reflection and refractive index are all joined

3. Snell's Law

   • N = SIN I / SIN R

4. Total internal reflection

   • If you keep increasing the angle of incidence, the angle of refraction gets closer to 90degrees
     • Eventually i reaches a critical angle for which r = 90degrees.
       • Above this critical angle you get total internal reflection
   • The angle of incidence is...
     • ...Less than the critical angle:- Most of the light passes out but a little bit of it is internally reflected
     • ...Equal to the critical angle:- the emerging ray comes out along the surface. Theres quite a bit of internal reflection
     • ...Greater than the Critical angle:- No light comes out. Its all internally reflected