Electromagnetic Spectrum

Electromagnetic Spectrum

The electromagnetic spectrum is a series of radiations that travel at the speed of light. We can see some of the spectrum, and this is called the visible spectrum. It includes a range of different colours, including:

• red
• orange
• green
• blue
• indigo
• violet

Surrounding the visible areas, there are different wavelengths that we cannot see. They all carry something.

Take a look at this YouTube video from Cognito about electromagnetism:

They all carry energy. If you take a power cord for example, you can put 12V current through it, and it will conduct along the wire. The wire can also have 240V current put through the wire, and it will travel from one end to the other. You may not necessarily see the current moving along, but it is there. This is similar to the electromagnetic spectrum.

Types of Radiation

There are several types of radiation that work at different waves. They include:

Radio: radio works using long wave (LW), medium wave (MW) and very high frequency (VHF). We receive the radio waves using an aerial system. The aerial at the point of transmission sends out the radio waves, and we receive it on a smaller aerial coming into the house or in the car.

Microwaves: you may use a microwave to heat up your food in. These waves are slightly smaller than those used by radio waves, but work on a slightly different frequency. They are also used for long-range communications.

Infrared: just outside of our visible range, infrared sits in the peripheral vision. It is used for things like night vision, your remote control and other devices that use a similar feature.

Visible light: these are the lights we can see - red, orange, green, blue, indigo and violet. In devices, you can visibly see photography, laser surgery and communication (in the form of optical fibres).

Interesting fact: Li-Fi is a type of wireless communication standard that uses light frequencies in the visible, ultraviolet and infrared parts of the electromagnetic spectrum.

Ultraviolet: let's say you go to a night club, and they have strobe lights. You're wearing a white t-shirt, and when you look down at it, it's glowing bright. That's ultra violet light. The Sun discharges it, and also we use it to test bank notes for forgery.

X-rays: when electrons hit a metal target really fast, they are called X-rays. Commonly found in hospitals, used for seeing your bones or inside your body, they can also be used to find hidden devices.

Gamma rays: the shortest wavelength that we cannot see is used in medical treatments, sterilisation of surgical equipment and can be used to destroy cells of a cancerous nature.

From radio waves having a long, low frequency wave, to gamma rays having a higher energy, more frenetic frequency and short wavelength, we have utilised a lot of the electromagnetic spectrum for every day use, as well as specific roles.

Types of Waves

There are also different types of waves that asociate with different types of radiation. They include:

• Longitudinal waves - a wave that moves depending on how the source is created. Sound is a good marker for this, and it can be demonstrated by using a slinky to show the movement of the wave.
• Transverse waves - the waves move at the same pace in uniform to each other. Imagine a rope on the floor, and you move it by lifting one end up at a time. It will move the wave to the other end, but in a uniform pattern.

End Note

We have learnt that there are different wavelengths that we can both see, and that we cannot see, and that they have varying frequency. We have also learnt that they are used in every day functions, like your TV remote, or your mobile phone, and even the radio. We also know that we can see some in visible light.