Light

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

How fast is 3 x 108 metres per second?

When light hits a surface, it bounces or REFLECTS off the surface. If light hits a smooth surface, it will bounce at a predictable angle. 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 curve inward - like a “cave” Close up – image is enlarged, right-side up. Further away – image is enlarged, but upside-down. The further away you move, the smaller the image gets.

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

Convex Mirrors curve outward The image is always smaller and right-side up. 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 Convex mirrors cause rays to DIVERGE or spread out.

Which is convex? Which is concave?

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

Lenses – curved transparent materials that refract (bend) light to make images Convex lenses Curve out Light rays bend together after passing through “e” in convex = together Notice that the light ray that strikes the lens straight on stays straight, but the ones striking the curved part angle together, the further away from the center the sharper the angle 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 Curves inward (like a cave) Light rays pass through and move apart “a” in concave = apart Again, notice the ray striking the center of the lens where there is less curve stays straight, but the rays striking away from the center angle more

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

What would happen if you put both of them together? Hmm….. Look at the top and bottom rays- not only further from the center, but they are coming in at an angle so they don’t bend as sharply

Blind spot

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