Refraction

• Law of reflection


  When light is reflected from a mirror, the angle of incidence is equal to the angle of reflection
• Diagram of light ray bouncing off a mirror

  1. Label both rays

  2. Label both angles

  3. Label the normal
• Type of reflection


  Specular reflection
• Diffuse scattering


  • Diagram showing diffuse scattering
• The light reflecting off the pencil is travelling first through the water and then through the air
• When the light leaves the water, it changes direction
• Refraction

  The phenomenon where light appears to bend when it passes from one medium to another
• When you run from land into water


  Your speed changes because you are entering a new medium
• Refraction


  • The speed of light is dependent on the medium it is travelling through
  • A ray of light refracts towards the normal when it slows down and away from the normal when it speeds up
  • The greater the change in speed, the bigger the bend
• Light travels in straight lines. When light rays pass into a different medium, the speed of the light ray changes. Light travels slowest in dense mediums. When a light ray enters glass having previously travelled through air, the speed of the wave decreases. This is because glass is denser than air. A ray of light refracts towards the normal when it slows down and away from the normal when it speeds up. The greater the change in speed, the more the ray deviates (changes) from its original path.
• Your brain thinks that everything travels in a straight line, so it sees the pencil as bent
• When you look at a rock in the bottom of a pond

  1. It appears to be above where it actually is

  2. This is because the light refracts when it travels from the water into the air

  3. It bends away from the normal when it enters the air

  4. This is because its speed increases
• States of matter in order of how quickly light can travel through them

  • Vacuum
  • Gas
  • Liquid
  • Solid
• When light rays enter a denser medium


  The speed would decrease, but the direction would stay the same
• Light rays slow down when they enter a denser medium
• The denser the medium, the more the light rays slow down
• When light rays enter a denser medium, they refract away from the normal
• The more the speed of the light ray changes, the bigger the bend is
• The angle of incidence is not equal to the angle of refraction
• Eye


  Convex lens
• Characteristics of concave and convex lenses

  • Curves outward
  • Curves inward
  • Separates light rays
  • Brings light rays together
• Investigating Refraction


  1. Independent variable

  2. Dependent variable

  3. Control variables

  4. Conclusion: how do the size of the angles of incidence and angles of refraction compare?

  5. What happens when you shine the ray box along the normal line?

  6. Compare the direction of the light travelling into the block and the direction of light rays coming out of the block
• Refraction and reflection


  Examples of everyday objects where light rays are a) reflected and b) refracted
• The shape of the glass block affects the refraction of light