Light Facts About Light Light travels in straight

Light

Facts About Light • • • Light travels in straight lines This creates shadows The speed of light is 300 million m/sec There is nothing faster Luminous objects make their own light e. g. the Sun • Non- luminous objects cannot be seen in the dark

Transparency • Transparent objects let lots of light through them • Name some transparent materials? • Glass, perspex, pure water, clean air • Translucent let some light through • E. g. frosted glass • Opaque do not let light through them • E. g. bricks, carpet etc.

Shadows • Light travels in straight lines • It can not travel through opaque objects • During a lunar eclipse the moon blocks the Sun’s light making an umbra (dark shadow on the Earth)

Shadows • To make a shadow bigger move the light source towards the object or move the screen further away • To focus a shadow move the object closer to the screen or away from the light source

How We See • We can see the light bulb because it is luminous • We can only see the battery because light is reflecting off it • If the light was switched off we would not see the battery

Reflection • Light bounces off some surfaces • Shiny surfaces like mirrors, polished cars, shoes, washed windows are excellent at reflecting light • Dull surfaces are poor light reflectors • When you look at your reflection in a pond you can see a clear image when the surface of the water is flat or even • This image can be destroyed by throwing something into the water making the surface rough and uneven

Reflection • The angle of incidence is equal to the angle of reflection • The incident ray is the ray going in to the mirror • The normal line is an imaginary line

Refraction • Light bends when it travels from one state to another • Light slows down when it goes into a more dense substance • It speeds up going into a less dense substance

Refraction • There is a normal line when light goes into the glass block • Light bends towards the normal when it goes into a more dense substance • It bends away when leaving the glass block

Dispersion • White light is made up of seven different colours • These colours combined are the visible colour spectrum • White light can be spilt using a triangular prism • Red is refracted least, Violet most

The Spectrum • Richard Of York Gave Battle In Vain • Red Orange Yellow Green Blue Indigo Violet • There are three primary colours Red, Green and Blue

Colours • We can see non- luminous objects because they reflect light • Objects can be different colours • A red shirt reflects red light and absorbs all other colours • A white shirt reflects all colours • A black shirt absorbs all colours and reflects no light

Colours • Coloured objects can either be seen (will look their normal colour) or cannot (appear black) • Filters can be used to separate the colours • The green filter allows only green light through it, the red filter allows only red light