MIRAGESMirages are actually optical illusions

They are usually seen on a very hot day and are a result of how light travels through air at different temperatures

The air directly above a hot surface is much hotter than air above itLight travels differently through materials of different densities (refraction)

Light is bent as it travels through the hotter air to your eye

pavement

Bent light path from skyEye assumes it’s coming from the pavement

So now the image comes from the pavement instead of the sky

What is supposed to be just blue sky now looks like blue water on top of the pavement

THE NATURE OF LIGHTA straight line stream of

particles as suggested by Isaac Newton, or … the movement of energy in wave

form?

We know that particles have mass Does light have mass?

NOT REALLY!!

So then it must be energy and travel in wave form

NOT REALLY!!

IT BEHAVES LIKE BOTH!!!

Light travels in straight lines suggestive of a beam of particles

because it can be blocked by objects

…. But it can also go through a substance, suggesting that it travels as

a form of energy

Albert Einstein suggested that due to the dual particle/wave nature of light, that energy and mass are interchangeable and can be converted one to another

E = mc2

E is energy, m is mass and

c is the speed of light

There are still lots of missing pieces in our understanding of the nature of light

WAVE NATURE OF LIGHT

VISIBLE LIGHT

Different wavelengths of light can be separated if white light is passed through a

transparent prism

A blue object absorbs all light wavelengths except blue which is reflected back at you

A red object absorbs all light wavelengths except red which is reflected back at you

The molecule inside chloroplasts which traps the sun’s energy for use in photosynthesis is called chlorophyll

Chlorophyll absorbs all light wavelengths except green which is reflected back

Black is the colour of nothing

White is the colour of

everything

RAINBOWSRainbows are caused by light

refracted and separated through millions of tiny water

droplets in the air

The water droplets are acting like prisms

The different colours in a rainbow blend one to the

next

They are not distinct and separate bands of colour

HOW WE SEE COLOUROur retina is a very thin layer of

light sensitive cells

The cells are of two different types

Rods and Cones

Rods detect the presence/absence of

lightCones detect colour and don’t work very well in the dark

There are three different kinds of cones: one detects red light, one detects green

light and one detects blue light

Colours besides red, blue and green are produced by different amounts of these colours combined together

This is slightly different than mixing paint colours together

Colour blindness is caused by an inadequate or weaker supply of a certain type of cone and is more prevalent in males than females

BEYOND LIGHT

RADIO WAVESLongest wavelength,

lowest frequency

INFRARED RADIATIONheat radiation

Anything that is warmer than its surroundings will emit infrared rays

Warmer areas are yellow, orange and red; colder areas are green, blue and black

VISIBLE LIGHT

ULTRAVIOLET RADIATION

Never look directly at the sun

U V light is damaging

Ow!

The ozone layer in the earth’s atmosphere blocks out much of the damaging U V radiation, however in recent years, the ozone layer has been thinning because of chemicals that we put in the air.

That leather look (and feel) is not a jacket

MELANOMA – TERMINAL SKIN CANCER

X RAYS

Broken dog leg

Dental x-rays showing fillings

Can easily pass through soft tissue like skin and muscle

GAMMA RAYSHighest frequency, shortest wavelength

Very energetic and very penetrating

Exposure to high doses of gamma rays causes cancer

Causes radiation sickness

EXTENDING NIGHT VISIONWorks two ways

Magnifying the small amount of light that is actually there or …

Capture and visualize the infrared radiation that is emitted

LASER LIGHT

Transmitting data between satellites with laser light

Concentrated light of a single wavelength

Very precise; so precise, it can cut glass and metal