The Speed Of Light: Unraveling The Mystery For Kids

KS2 students can learn about light, where it comes from, and how it travels. Light travels in straight lines and is a form of energy that we can detect with our eyes. When light enters our eyes, our brain interprets this into images we can see. Light travels from the source to an object, which reflects the light into our eyes so we can see it. Light travels at incredible speeds – nearly 300,000 km in 1 second! That's 7 and a half times the length of the equator in the same time it takes you to read this sentence.

Light travels in straight lines

Light travels fastest in a vacuum. It can travel through space, but when it enters a different material, such as air or water, it changes speed and direction. This is called refraction. Light can also be bent by gravity, which is known as gravitational lensing.

Although light travels in straight lines, it can be affected by diffraction, which is when light waves spread out as they travel. This means that different parts of the light beam bend in different directions, causing the beam to spread out. Diffraction is caused by obstructions in the light's path. However, the effects of diffraction are usually negligible in everyday life.

Light is reflected by objects

Reflection involves two rays: an incoming or incident ray and an outgoing or reflected ray. The law of reflection states that the angle of incidence is equal to the angle of reflection. This law is obeyed at all interfaces, such as the surface between air and water, or glass and water. Each time a ray of light strikes a boundary between two materials, some of the light is reflected.

Different surfaces reflect light to varying degrees. For example, a mirror reflects almost all the light falling on it, whereas a stone does not, which is why a mirror causes glare.

Colour is also an important aspect of light reflection. The different colours we see are created by light shining on objects, with different colours being reflected back into our eyes. For example, a red object reflects red light and absorbs all the other colours of light. Similarly, a blue object reflects blue light and absorbs all the other colours. The colour black is a little different, as it absorbs all the colours of light and reflects very little, making it appear very dark.

Light is a form of energy

Light is a form of electromagnetic radiation of a wavelength that can be seen by the human eye. It is a type of kinetic energy. Kinetic energy is energy in movement and includes electrical energy, heat, light, and sound. Light energy is very fast – in fact, nothing travels faster. The speed of light in a vacuum is 299,792 kilometres per second.

Light travels in straight lines from its source. It reflects off objects in straight lines, too. This is how a smooth, shiny mirror creates a reflection. When light reflects off a rough surface, it goes in different directions, so you don’t get a sharp reflection. Think about how different a reflection is in still water compared to water with waves or ripples.

When light travels through different materials, such as water or air, it changes direction slightly. We call this refraction. This is when light changes speed as it travels through different materials, which can cause it to bend or change direction.

Light travels through different materials

Light travels in straight lines. But when it moves from one material to another, such as from air to water or water to air, it changes speed and direction. This is called refraction.

When light travels through different materials, it behaves differently depending on the type of matter it comes into contact with. Light passes directly through transparent materials like air or water. In these cases, light is slowed down, but it doesn't stop it from passing through.

Opaque objects, like animals or books, completely reflect light. Light doesn't pass through these objects at all.

Then there are translucent objects, which do a bit of both—they let some light through while reflecting or scattering the rest.

When light passes through transparent materials like water or glass, it bends or turns. This is because different materials have different qualities. As light passes through, its wavelength changes, but not its frequency. As a result, the direction and speed of the light wave change, and the light appears to bend.

A great example of refraction is a prism. A prism takes white light from the Sun and separates it into its different colours. Each colour of light is refracted to a different angle.

Light is made up of many colours

The light from the Sun, which we often perceive as white, is actually a combination of many different colours. We call this full range the colour spectrum. The colours of the spectrum are the same as those of a rainbow, which is created when sunlight passes through water droplets in the air and is split into different colours.

The colours of the spectrum range from red, at the longer wavelength end, to violet, at the shorter wavelength end. White light is made up of all the colours of the rainbow because it contains all wavelengths. When we see an object as a particular colour, it is because that object has absorbed all the other colours and reflected that specific colour back to our eyes.

For example, a red shirt appears red because the dye molecules in the fabric have absorbed the wavelengths of light from the violet/blue end of the spectrum, and only red light is reflected. If only blue light is shone on a red shirt, it would appear black because the blue light would be absorbed and no red light would be reflected.

Black objects appear black because they absorb all colours of light, so none is reflected. On the other hand, white objects reflect all colours of light, which is why they appear white.

Our eyes detect light through the retina, which contains two types of photoreceptors: rods and cones. The cones detect colour, while the rods only allow us to see in black, white, and grey. This is why, when it is very dim, we cannot see colours at night.

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