Light (Natural)

Light is a form of radiant energy that we can see with our eyes and is transferred through radiation. It’s made up of microscopic particles that travel in the form of electromagnetic waves. Without light, we wouldn’t be able to see.

The Sun is a natural source of light, but many artificial light sources have been invented too. For example, light bulbs and computer screens both produce light energy.

Light phenomena

Light phenomena are observable events that occur when light interacts with matter.

Light travels in straight lines. When we put an opaque object in front of light, we can see a shadow behind the object. Light is blocked by the object, and forms the shadow.

The shadow has the same shape as the object because the waves of light that aren’t blocked travel in straight lines.

Light travels very fast. It is the fastest thing in the universe. Nothing can travel faster than light. The speed of light is 300.000 kilometres per second.

Objects react to light in different ways.

A transparent window. It doesn't block
the light

This glass is transparent: it doesn’t block the light. Imagine a house with no windows. It would be dark.

Curtains like this are translucent

The curtains are made of a translucent material: they block some light, but some light passes through the material.

Thick curtains or even a wall can be opaque: it blocks the light completely.

Uses of light energy

We use light energy in many ways.

• We use light from the Sun to see and to produce electrical energy with solar panels.
• We use light energy to see at night. Light energy enables us to see things on television and computer screens.
• Lights can indicate when a machine is switched on.

Solar panels

Reflection occurs when light energy bounces off a surface and changes direction. Reflection is one of the basic laws of light.

We know that light travels in straight lines. However, some surfaces, like mirrors, cause the light to change direction.

Smooth surfaces, such as glass, metal or the surface of a large body of water, reflect light better than rough surfaces, such as wood or stone. For example, when light energy hits a mirror, it’s reflected. As a result, we see a reflection in the mirror.

Light travels in a straight line from the object to the mirror.

The mirror reflects the light, causing it to change direction.

A boy or a girl can see the reflection of the object in the mirror When light passes from one medium to another, for example, from air to water, the light energy changes direction. This process is called refraction.

Water changes the direction of the light rays that pass through it.

When we look at the straw, it appears to be bent. This is because the water is refracting the light.

White light

White light is made up of all the colours combined together. We can separate white light into colours by refraction. The colours are not refracted equally, so we see all the different colours. For example, prisms reffract light. As a result, we see the colours that make up white light.

Activities

1. Match to make sentences in your notebook:

a) Reflection causes light to...
b) Refraction causes light to...
c) White light is made up of...

1. ... bend as it passes through a different medium.
2. ... all the colours combined together.
3. ... change direction when it hits a surface.

2. With someone from your family, predict which of these materials will be opaque, transparent and translucent.

Aluminium foil, cardboard, a sheet of paper, cling film, a plastic water bottle, a white T-shirt
Use a torch to test your predictions. How many of your predictions were correct?
Make a table to show your predictions and your results.

3. Write down three important features of light.

4. Once you finish complete the assignment on milton. 

Enjoy! 😎