Isaac Newton was an English scientist. He was born in 1642 and he died in 1726.
Isaac Newton accidentally discovered
gravity when he was under a tree and an
apple fell on his head.
Gravity is the force that the Earth has. It pulls objects
toward it.
The gravity of the Sun and the Moon pulls the Earth.
That is why we have two
low tides
and two high tides
He also showed that a white light through a prism can turn into seven
colours.
They can be natural like the Sun, stars, lightnings, etc.
They can be artificial like light bulbs, torches, candles, etc.
CHARACTERISTICS OF LIGHT
1. Light travels at 300.000 kilometres per second.
If the distance between our Sun and the star of Alamak is 350 light years, the Sun is
3.452.929.200.000.000 kilometres away from Alamak.
2. Light is white but when it is refracted through a prism, it turns into 7 colours.
When there is sunlight and it rains at the same time, rain drops act like a prism. That is why we
can see the rainbow.
3. Light travels in a straight line.
4. When there is an obstacle, light can be:
Absorbed. Black clothes absorb light, so it is quite
uncomfortable to wear black clothes in summer.
Reflected. Reflection happens when light bounces off objects like mirrors.
Refracted. Refraction occurs when light changes direction, for example when it enters water.
MATERIALS AND LIGHT
Objects can be: TransparentTranslucent
Opaque
Transparent materials:All light can pass through them.
We can see clearly through them.Examples: glass.
Translucent materials:Some light can pass through them.We can see partially through them.
Examples: sunglasses.
Opaque materials:No light can pass through them.We cannot see through them.
Examples: wood, paper, walls, etc.
Opaque objects can absorb or reflect colours.
A tomato is red because it reflects the red and absorb the rest of the colours.
A pear is green because it reflects the green and absorbs the rest of the colours.
Black objects absorb all the colours but they don't
reflect any colours.
White objects reflect all the colours but they don't absorb any colours.
Snow reflects colours but doesn't reflect any of them.
REFLECTION
Reflection happens when light bounces
off and object.
When light hits a smooth surface, the rays reflect in
the same direction.
When light hits a rough surface, the rays reflect in different directions.
REFRACTION
Refraction happens when light changes direction because it has moved from one
substance to another.
Here, light has travelled from air to water.
But refraction also happens when: A light goes through a prism
Light travels from one substance to another
Light reaches lenses
Lenses are made of a
curved surface that refracts
light.
We can find lenses in :
TELESCOPES