Waves

YOU ARE LEARNING:

Properties of EM Waves

All electromagnetic waves are transverse waves that travel at the speed of light. They form a spectrum that ranges in frequency and wavelength.

Light waves are electromagnetic waves with different properties, depending on the frequency and wavelength. The range of these waves make up the electromagnetic (EM) spectrum.

EM waves are the only waves that can travel through a vacuum - **** they do not need matter to carry them, unlike sound waves for example.

All light travels at the same speed in a vacuum (or air). Can you remember what this is?

The reason EM waves are called electro-magnetic is because they are made up of oscillating electric and magnetic fields, instead of matter.

You do not need to know the details of this, but this is the reason they can travel through a vacuum.

What kind of wave is a light wave?

All electromagnetic waves are transverse waves. Which of these statements correctly describes the properties of transverse waves?

To summarise, electromagnetic waves are all transverse waves that travel at the speed of light.

What is the equation that links the speed of a wave with its frequency and wavelength?

If an electromagnetic wave has a very long wavelength, will its frequency be small or large?

Here we can see the full electromagnetic spectrum. The wave types are grouped in terms of their wavelength and their frequency.

As you move down, wavelength increases and frequency decreases.

What type of EM wave has the shortest wavelength?

What type of EM wave has the lowest frequency?

There are lots of different ways to remember the order of the EM spectrum.

One way is to remember the phrase in the image. See how the first letter of every word matches the first letter in each section of the EM spectrum.

Our eyes can only detect a limited range of frequencies of EM radiation, that is visible light. The visible spectrum is a continuous range of colours within the EM spectrum. Which colour has the lowest frequency?

What colour corresponds to light with a wavelength of $600nm$ ?

The energy of an electromagnetic wave is proportional to its frequency. Out of these types of electromagnetic radiation, which has the highest energy?

To sum up

EM waves are all transverse waves that travel at the speed of light, $3\times10^8\:m/_s$ .

One way to learn the order of the spectrum is by remembering the phrase

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