Light - Reflection

• Incident ray


  Ray of light that is pointing towards and striking a surface
• Reflected ray


  A ray that bounced off a surface
• Normal


  A ray that is incident at 90° degrees to a surface
• Specular reflection


  • Occur when a light bounces off a very smooth surface and is reflected at the same angle
• Diffuse scattering


  • A scattering that arises at any departure of a material structure from that of a perfectly regular lattice
• Law of reflection - Reflected ray


  The angle it goes in = The angle it comes out
• Angle of incidence


  The angle between the incident ray and the normal
• Angle of reflection


  The angle between the normal and the reflected ray
• Rough surfaces


  • Diffuse reflection - Reflected in all directions
• Smooth surfaces


  • Specular reflection - Reflected in the same angle it came from
• The image is formed because light reflects off the mirror so that the angle of incidence is equal to the angle of reflection
• The light hits the wall and is reflected at lots of different angles. The light needs to reflect in a regular way to form an image
• Refraction


  The change in direction of a ray or wave as a result of its change in speed
• Refraction


  1. Light travels from one medium to another

  2. Light slows down when it goes on

  3. Light speeds up again when it comes back out

  4. Direction changes twice

  5. Light bends towards the normal when it goes in

  6. Light bends away from the normal when it comes out
• Incident ray


  A ray of light that is pointing towards and striking a surface
• Normal


  A ray that is incident at 90° to a surface
• Angle of reflection


  The angle between the normal and the reflected ray
• Law of reflection


  The angle of incidence equals the angle of reflection
• Specular reflection


  When rays of light are reflected off a smooth surface in the same angle it came from
• Diffuse reflection


  When light hits a rough surface and is reflected in all directions
• Lens


  There are 2 lenses in the body, the lenses are either a convex or converging lens - it focuses the light and enables you to see
• Focal point


  The point where rays cross
• Convex lenses


  Produces real images - can be used to put up on the screen in a camera
• Concave or diverging lens


  It spreads light out. Light is refracted at both surfaces of the lens. The image in a concave lens is always virtual - cant put it on a screen
• Pupil


  The hole in front of the eye where light goes in
• Iris


  The coloured part of the eye
• Cornea


  The transparent layer at the front of the eye
• Photoreceptors: rods and cones


  Rods: sensitive to movements and dim light. Cones: Sensitive to bright light and color
• Vision


  1. Light reflected from an object enters the eye through the pupil

  2. Iris controls the size of the pupil

  3. The cornea and the lens focus the light onto the retina

  4. Image of the object is formed on the retina

  5. Image is inverted but the brain sorts it out
• Pinhole camera


  1. Light enters the camera through the pinhole

  2. An image is formed on the screen - just like the retina
• Further from the object

  The smaller it looks