• Light travels from a luminous source (one that gives out light - shines - is usually very hot!)
• Light travels at a very high speed - much faster than sound - the fastest speed possible 300 million metres per second (about a million times faster than sound!).
• Light travels in a straight line path and that gives rise to shadows (done at KS2)
• The path of light can be represented by rays - see ray diagram rules
• Materials may be transparent (completely 'see-through' - allowing you to see an image through them), translucent (allows light through but the rays all get mixed up and you can't see a clear image through them) or opaque (lets no light through at all)
• Light may be absorbed, transmitted or reflected
• We see non-luminous objects because light (from the luminous source) is reflected (or scattered) off them and enters our eyes after being redirected from the object. We therefore see the light that has been scattered/reflected but not the light that has been absorbed.
• How the eye works - see cyberphysics diagram
• We represent the path of light by rays (straight lines with an arrow on them)
• Light is reflected from plane surfaces in a predictable way- angle of incidence = angle of reflection.
• When light is reflected from plane surfaces an image is formed that is erect, virtual, same size as the object, as far behind the mirror as the object is in front
• For how to draw image formation diagrams for a plane mirror.
• Refraction: light changes speed at a boundary between two different media and this makes its pathway change direction. If it slows down it bends towards the normal. If it speeds up it bends away from the normal.
• Real and apparent depth - see cyberphysics diagram
• White light can be dispersed to give a range of different colours
• The spectrum has seven colours: red, orange, yellow, green, blue, indigo, violet
• Coloured filters absorb some of the wavelengths in white light
• Colour addition: how coloured light can be combined to produce new colours: primary RGB - secondary YCM
• Colour shadows - application of colour addition and KS2 shadows!
• Primary colours are red, green and blue because those are the colours that stimulate the three types of cone we have in the eye.
• How coloured objects appear in white light and in different colours of light
• Why the primary colours for paint mixing are different from the primary colours of light mixing - paint pigment mixing.
• Description what happens to a beam of light when it encounters a range of materials (is it transmited (let through), refracted (are the rays bent?), reflection ('bounced of'f so i = r - this happens with shiny surfaces), scattered (bounced off so the rays get jumbled up and no reflection can be seen - this happens with dull surfaces) absorbed or partly absorbed (coloured))