Light KS3 Y7

Light KS3 Y7

1. Lumination

   • Luminous means a light source that emits light
   • Illuminated means an object on which light shines and from which light may be reflected
   • Opaque is an object where no light can pass through
     • All light is absorbed or reflected
   • Translucent is an object where some light passes through
     • It absorbs and reflects some light
   • Transparent means an object where all or most light passes through
     • Very little or no light is absorbed or reflected

2. Shadows

   • Point source is where light rays are emitted radially.
   • Non-point source is where rays from different part of the source form different overlaping shadow.
   • Umbra is a complete shadow (all rays blocked).
   • Penumbra is partial shadows, (some rays blocked).

3. Pin-hole camera

   • The image will be inverted
   • Small pin hole: focus but dimmed image
   • Large pin hole:unfocused but brighter image
   • Rays pass through the middle of the gap.
   • If there are two gaps, then there will be two images

4. Reflection

   • When light shines on an object, it is either transmitted, absorbed or reflected
   • A normal mirror is a flat plane and a regular reflector
   • An uneven shiny surface is a diffuse reflector
   • A line separates line into two and is called a normal line
   • The incident ray is the same angle as the reflected ray
   • If there was an odd number of mirrors, the image would be laterally inverted, upside down
   • The virtual ray is on the opposite side of the mirror and is in line with the reflection.
   • The virtual image is the image on the other side of the mirror

5. The visible spectrum

   • White light is a mixture of all the colours in the visible spectrum
   • Richard Of York Gave Battle In Vain (Red , orange, yellow, green, blue, indigo, violet)
   • When a white light travels through a prism it splits into its component colours
   • Each component bends through a different angle.
   • Red bends the least and violet bends the most
   • Some materials only reflect or transmit certain colours and asborbs the rest
   • The bending is called refraction and the splitting is called dispersion
   • In additive, red, green and blue are the primary colours
     • Yellow, magenta and cyan are the secondary and altogether the secondary colours make white.
   • In the subtractive, it is the opposite and all of them create black.