In Photosynthesis light energy is changed to
chemical energy in growing plants.The
vegetables we get from photosynthesis we use
to change into other forms of energy.
Solar cells covert light energy to electrical
energy. Solar cells can power satellites,
calculators and parking meters in cities and
Light is used to turn electrical systems on and
off.Heating systems are turned on during the
day when needed and turned off again in the
evening when it gets dark.
Light is one of the forms of energy we get from the sun.
Light energy is coverted to other forms:
To show light is a form of energy you must show that light
can move something. (Crookes Radiometer can be used to
Light travels at 300000000 meters in one second!
Light travels in straight line.We can prove this by using a bulb and
three pieces if cardboard.You take the cardboard and cut a hole in
the exact same place in the middle of the peieces, then you move the
three pieces of cardboard in a straight line with the light bulb, you
will see that a strip of light shines through all the peices,however if
you move one of the pieces of cardboard you will find that the light is
cut off.This proves that light travels is straight lines.
Shadows:Shadows are formed when light
coming from a source is blocked.The shadow is
then similar in outline to the object blocking the
Example: Place your fingers between a candle
and a screen and notice that as you bring
yourfinger closer to the candle more light gets
blocked out and the shadow gets bigger
Reflection:Is the boucing of light from a surface. Example: Mirrors, Perriscope
We can see objects because some of the light which leaves the objects hits our eyes.
Luminous Objects: Are a source of light.
Examples: The Sun, A light bulb, a candle.
Non-luminous objects: Are seen as a result of light reflected from them.
Examples: Everything else (not emitting their own light)
A way of showing Reflection is using a ray box and a
mirror, Shine the ray box on the mirror and see that
the ray of light bounces off the mirror and reflects
back in the same direction.
Refraction:Is the bending of light as it passes from one medium to another.
A way to demonstrate
refraction is to shine a ray
of light into a glass block
and notice that it bends
on the way in and also on
the way out.
A lens is a curved pice of glass
used to bend (refract) light
inwards or outwards.
Refreaction of light through a Lens
Converging Lens (Convex Lens): Bends light so it converges to a point.
Diverging Lens (Concave Lens): Bends the light so that it diverges outwards.
Dispersion: Is the breaking up of white light into its individual colours (called a spectrum)
White light is made up of different colours which can be separated by dispersion.
To produce a spectrum of white light use a bulb, a prism and a screen. Turn the prism slowly until
a spectrum is formed on the screen.