Colour & Filters D. Crowley, 2008

Colour & Filters To know how coloured filters work, and to be able to predict how these will affect the appearance of an object

Light Key Words Solve the following anagrams of light key terms… Suonmiul Nno-minluous Depisrdes Detcfrare Ferletced Eencidnci Glane Msurtcpe Rooluc Luminous Non-luminous Dispersed Refracted Reflected Incidence Angle Spectrum Colour

Colour Look at the following colours – why do we seem them? Object Filter Look at the following colours – why do we seem them? Coloured objects reflect some colours and absorb others Red absorbs all colours, except red which it reflects Green absorbs all colours, except green which it reflects Blue absorbs all colours, except blue which it reflects Black absorbs all light, reflecting none… White reflects all light, absorbing none…

Colour Now look at the following colours through a filter… Object Filter Now look at the following colours through a filter… Filters let certain colours of light pass through, but absorb all other colours Using the different filters look at the colours on the board / around the room and try and work out what the filter is doing – i.e. what is a blue filter doing? What about a red filter etc…

Colours A red filter absorbs all colours… …apart from red light A blue filter absorbs all colours… …apart from blue light A green filter absorbs all colours... …apart from green light

Colours A magenta filter absorbs all colours… …apart from red and blue light A cyan filter absorbs all colours… …apart from green and blue light A yellow filter absorbs all colours... …apart from red and green light

Light Filters can make objects appear different colours than they actually are This is because they only let a certain type of light through (e.g. red filter only lets red light through) Looking through a red filter can therefore be described as looking at something in red light Red light shines on the ball The red ball reflects the red light, appearing red

Red Ball What does a red ball appear like in different light, e.g. in green, blue and magenta light? In green light Green light shines on the ball The red ball absorbs the green light, so no light is reflected, and the ball appears black

Red Ball What does a red ball appear like in different light, e.g. in green, blue and magenta light? In blue light Blue light shines on the ball The red ball absorbs the blue light, so no light is reflected, and the ball appears black

Red Ball What does a red ball appear like in different light, e.g. in green, blue and magenta light? In magenta light (mix of red and blue) Magenta light shines on the ball The red ball absorbs the blue light and reflects the red light, appearing red

Filter

Light Questions

Light Answers Light cannot travel through a stone Luminous source - lamp Opaque object - desk, cup, book etc… Transparent object - glass, window etc…

Light Answers Box B Normal Light is dispersed in all directions