Makinglight work

Like all forms of energy, light has theability to change the properties ofsubstances. For example, sunlight canchange the temperature of a surfaceand it can fade the colourful posters inshop windows over time. Light can alsobe transformed into other forms ofenergy. In your own eyes, light istransformed into chemical andelectrical energy to send messagesto your brain about what you arelooking at. Visible light is only onesmall part of a type of energy calledelectromagnetic energy.

Light is E

nerg

y

List the 7 types of light

electromagnetic radiation

List the colours of the rainbowWhen will you normally see a rainbow?

The electromagnetic spectrum?There is a range of electromagnetic energy,called the electromagnetic spectrum, whichincludes light we can see and light wecannot see. An example of light we cannotsee is radio waves. This type of light sendsenergy through the air that can be collectedby our radios and transformed into sound.Radio waves are low energy waves. However,some forms of electromagnetic energy, suchas ultraviolet light, have enough energy toburn us.

http://www.sanfranciscosentinel.com/wp-content/uploads/2008/05/skin-cancer.jpg

http://www.cancer.org.au/cancersmartlifestyle/SunSmart/Aboutskincancer.htm

Electricity from lightThe photovoltaic cells of a solarpanel create useful electricity directlyfrom light. The electrical energy from asolar panel is available because light itselfis a form of energy. The light energy istransferred to electrons within the siliconwafer that makes up each solar cell.These electrons are freed from the atomsthat they are part of. These `free'electrons then go on to become part ofan electrical current that we can use aselectrical power.

List some everyday

things that use a

photovoltaic

The Hubble Space Telescope

Types of Light

Ultraviolet radiation, alsocalled ultraviolet light, ismore energetic than visiblelight. As a result, it cancause chemical changes inmany substances, includinghuman skin. Sometimes suchchanges can be harmful.Exposure to ultravioletradiation in sunlight cancause sunburn. Long-termexposure to the Sun'sultraviolet radiationincreases your chances ofskin cancer. Some sunscreencontains chemicals thatabsorb the ultraviolet lightbefore it can damage thesurface of your skin. Others,like zinc oxide, block theultraviolet light.

X-rays are more energeticthan ultravioletradiation. They can alsocause chemical changeand can, therefore, bedangerous to livingorganisms. Because x-rayshave a lot of energy, theycan penetrate somematerials that are opaqueto visible light. The softtissues of the human bodyare transparent to x-rays,but bones are not. Thismakes x-rays a useful toolfor doctors wanting to lookinside our bodies.

Gamma rays are the mostenergetic and, therefore,the most dangerous formof electromagneticradiation. Gamma raysare also very penetrating.They can pass throughmany materials,including many metals.It requires a thick layer oflead to absorb these rays.Some stars give outenormous amounts ofgamma waves in a shortburst. Astronomers callthese `gamma-ray bursts'.They are among the mostenergetic objects in ouruniverse, a million trilliontimes brighter thanour Sun.

Other important types of light

The speed of lightAll forms of electromagnetic energy move through thevacuum of space with the same speed. The speed of light;300 000 kilometres per second. That's about seven times around theworld in one second! Scientists often use the letter `c' to denote thespeed of light in a vacuum.Einstein's Equation

How long would it take a flash of light to travel from Australia to the UK? How long does it take light to travel from the Sun (150million Km away)

Instructions for making a Pin Hole Camera

Make your ownpinhole cameraYou will need:a `tin' with both ends removed tomake a hollow cylinderaluminium foilgreaseproof or tracing paperelastic bands or sticky tapea pin.· Stretch the aluminium foil acrossone opening of your tin and thegreaseproof paper across theother.· Fasten the foil and paper withsticky tape or an elastic band.· Make a small hole (using your pin)in the centre of the foil.