Optics What is Light?

Light: A wave of energy that travels in straight lines which illuminates things.

Light travels at 300 000 km per second. (or 3 000 000 000 m per second) If light circled around the surface of the earth, it would travel 71/2 times around the earth in one second.

travels through different types of mediums (materials) Transparent mediums - All light passes through Eg. Window (plate of glass)

- some light passes through, but not all 2. Translucent: - some light passes through, but not all Eg. Stained glass

3. Opaque: - no light passes through object Eg. Wood, walls (drywall/cement)

Class Activity Can you think at least 3 everyday objects of each: transparent, translucent and opaque?

There are many different types of light emitted There are many different types of light emitted. The wave of each type has a different wavelength.

Electromagnetic Waves DO NOT COPY DOWN Believe it or not, you are being “showered” all the time, not by rain but by waves. 9

All waves are included on Electromagnetic Spectrum :

Different Wave Uses: Radio waves: TV signals, Cell phones Microwaves: microwaves, radar guns Infrared waves: burglar alarms, infrared goggles, night vision Visible Waves: Rainbows, Astronomy, human vision Ultraviolet waves: Disinfect drinking water, Sun Rays, detective work, Gone in 60 Seconds car list X-rays: Customs at airports to check luggage Gamma rays: Very dangerous, used to kill cancerous cells

Infrared Demo: Who has a cell phone?

Visible Light Spectrum: Light waves that we can see Different wavelengths emit different colours. ROY G. BIV are the colours we can see, if all wavelengths are shone together, white light is produced.

Spectroscopes Can you see the colours?

Colour Wavelengths

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