Light is a form of energy. Light is electromagnetic radiation that can be seen by the human eye. The electromagnetic spectrum is the range of frequencies of electromagnetic radiation according to the wavelengths and frequencies. 

Light is essentially a stream of photons. Photons are packets of energy that travel with wavelike properties at the speed of light. Light travels the fastest in the universe.

Light has a wavelength, frequency, and speed. We measure light’s wavelengths on the electromagnetic spectrum.  Different wavelengths produce different coloured visible lights. Light is made up of all the colours mixed together. A prism can be used to break up white light to reveal the different colours it is made up of. These colours include red, orange, yellow, green, blue, indigo, and violet. When light travels through a glass prism it hits it at an angle; this results in the different wavelengths of light slowing down by different degrees so each colour has a different angle of refraction. This is how a glass prism allows us to see all the coloured that make up white light. 

Refraction is when light waves bend as it passes from one transparent medium into another. The light bends due to the change in speed. For example, light travels faster through air and slower through water. 

This is the reason we see rainbows because the droplets of water in the air cause the light to split up into colours it is made from just like a prism. 

The colour we see depends on what is being reflected back or absorbed by the object. 

For example, a red bag is red because it absorbs all other colours except red. It reflects red back, so you see the colour red.

This is the same for other colours too, for example, a car is green because it absorbs all other colours except green. It reflects green back, so you see the colour green. 

Objects that reflect all wavelengths of light appear white, whereas objects that absorb all wavelengths of light appear black. 

For transparent objects such as glass, the light is not reflected the same way it would with a solid object. Instead, the light bends because light travels at different speeds in different mediums. This process is called refraction. 

Humans are only able to see visible light, whereas some animals and insects can see more than just visible light; therefore, they can see many different colours that we can’t. 

Light is made up of all the colours mixed together. A prism can be used to break up white light to reveal the different colours it is made up of. These colours include red, orange, yellow, green, blue, indigo, and violet. When light travels through a glass prism it hits it at an angle; this results in the different wavelengths of light slowing down by different degrees so each colour has a different angle of refraction. This is how a glass prism allows us to see all the coloured that make up white light. 

Darkness is when there is little or no light. 

The retina is the layer at the back of the human eye. It is the layer which contains millions of light-sensitive cells called rods and cones, alongside nerve cells that receive and organise visual information. Rods allow you to see light, and cones allow you to see colour. There are three types of cones: red, green, and blue. The different types of cones respond to different different wavelengths of light. Short wavelengths stimulate blue cones, and long wavelengths stimulate red cones. These specialised cells in the retina convert light into signals that are then sent to the brain via the optic nerve.  

Did you know some people are colourblind?

This is when one type of cone is missing from the retina or it doesn’t work. 

A light source is something that makes light. Light sources can be natural or artificial. 

Natural light sources exist by nature.

Examples of natural light sources are the sun, fire, and lightning. 

How does light travel?

Light travels very fast in a straight line. Light can be reflected off surfaces of objects around it. This reflection of light from an object is what allows us to see.

Light reflects from a surface at the same angle that it hits. It is important to know how light travels as this helps us understand how objects are seen.

How are objects seen?

Light can travel directly from the source to the eye which allows us to see the object.

For example, light made by a fire travels directly to the eye. 

How does light travel?

Light travels very fast in a straight line. Light can be reflected off surfaces of objects around it. This reflection of light from an object is what allows us to see.

Light reflects from a surface at the same angle that it hits. It is important to know how light travels as this helps us understand how objects are seen.

How are objects seen?

Light can travel directly from the source to the eye which allows us to see the object.

For example, light made by a fire travels directly to the eye.  👱‍♂️ ⟵ 🔥

Objects that don’t produce light themselves can be seen because they reflect light from another source. When the light enters the eye a message is sent to the brain, and the brain interprets what it is seeing. 

For example, the light travels from the sun to the tree. It is reflected and then travels into the eye. 👱‍♂️ ⟵ 🌲 ⟵ ☀️

Light can only travel in a straight line; however, it is possible to use reflective objects such as mirrors. This allows light to be reflected, changing the direction which makes it possible to see things that would normally be out of sight. 

An example of this is a periscope. A periscope is a piece of equipment used in submarines to see what is happening above the water. The mirrors used in a periscope reflect the light travelling through it and reaches the eye. So this allows them to see anything that is above the water.