Light Facts l Light is energy electromagnetic energy

Light

Facts l Light is energy – electromagnetic energy (energy that is electric and magnetic) l Travels in a straight path unless…it goes through a new material (medium) then it may bend or slow down l Travels in waves l Travels VERY fast! l The speed of light: 3 x 108 m/s

How fast is 3 x 108 metres per second?

l When light hits a surface, it bounces or REFLECTS off the surface. l If light hits a smooth surface, it will bounce at a predictable angle. l If light hits a rough surface, it bounces off at all kinds of angles.

Look at how the surface affects these water reflections.

The Law of Reflection states that: the angle of incidence (i) equals the angle of reflection (r) -

Concave mirrors l curve inward - like a “cave” ¡Close up – image is enlarged, right-side up. ¡Further away – image is enlarged, but upsidedown. ¡The further away you move, the smaller the image gets.

Concave mirrors cause rays to CONVERGE and meet at a focal point

Convex Mirrors l curve outward l The image is always smaller and right-side up. l Used for side view mirrors on cars, security mirrors to prevent shoplifting, and on tight bends in the road to give a wide angle of view.

Convex mirrors cause rays to DIVERGE or spread out.

Which is convex? Which is concave?

How light passes through objects l Opaque ¡ completely blocks light from coming through l Translucent ¡ Lets only part of the light through ¡ View is blurry l Transparent ¡ Allows light to pass through with almost no disturbance ¡ Can be clear or colored ¡ Clear view

l Lenses – curved transparent materials that refract (bend) light to make images l Convex lenses ¡Curve out ¡Light rays bend together after passing through ¡“e” in convex = together focal length

Convex lens – the rays bend together • If the lens is close to your eye, the image you see will be right-side up and enlarged. • If the lens is further away, the image will be upside down.

Concave Lenses l Curves inward (like a cave) l Light rays pass through and move apart l “a” in concave = apart

Concave Lens l The image you see is always smaller and right-side up.

What would happen if you put both of them together? l Hmm…. .

Blind spot

Parts of the eye and their functions l Cornea – thin clear covering over the front of the eye. l Pupil – hole in the centre of the iris, it changes size in bright light and dull light l Iris – coloured part of the eye, makes the pupil bigger or smaller l Lens – focuses light onto the retina l Retina – cells at the back of the eye that can detect light l Optic nerve – carries message from the retina to the brain.