Wavelength & the EM Spectrum

Red has the longest wavelength whilst violet has the shortest.

The unit used to measure wavelength is the metre. Because the size of electromagnetic waves varies, different prefixes are used to aid measurement. Here are six examples: kilometre, centimetre, millimetre, micrometre, nanometre and picometre.

Yes! Gamma rays have the shortest wavelengths within the electromagnetic spectrum.

Blue and violet are two of the colours in the visible spectrum with the shortest wavelengths.

The wavelength of an electromagnetic wave is a measurement of the length of a single oscillation of the wave.

Energy is a property of matter and fields, which can be transferred between systems or transformed into different forms but cannot be created or destroyed.

• Everything contains energy including all forms of matter and so all objects.
• Energy is evident in all forms of movement, interactions between, and changes to the forms and properties of matter.
• At an atomic level, energy is evident in the movement of electrons around the nucleus of an atom. Energy is stored in the nucleus of atoms as a result of the forces that bind protons and neutrons together.
• Energy can be transferred between objects, and converted from one form to another, but cannot be created or destroyed.
• Everything in the universe uses energy in one form or another.
• When it comes down to it, matter is energy.
• Light has energy but no mass so does not occupy space and has no volume.
• Energy is often described as either being potential energy or kinetic energy.
• Energy is measured in joules.

 

Wavelength measures a complete wave cycle, which is the distance from any point on a wave to the corresponding point on the next wave.

• While wavelength can be measured from any point on a wave, it is often simplest to measure from the peak of one wave to the peak of the next or from the bottom of one trough to the bottom of the next, ensuring the measurement covers the whole of the cycle.
• The wavelength of an electromagnetic wave is usually given in metres.
• The wavelength of visible light is typically measured in nanometres, with 1,000,000,000 nanometres making up a metre.
• Radio waves, visible light, and gamma waves for example, each have different ranges of wavelengths within the electromagnetic spectrum.

An electromagnetic wave carries electromagnetic radiation.

• An electromagnetic wave describes electromagnetic radiation as it propagates from a light source, travels through space and encounters different materials.
• Electromagnetic waves can be imagined as synchronised oscillations of electric and magnetic fields that propagate at the speed of light in a vacuum.
• Electromagnetic waves are similar to other types of waves in so far as they can be measured in terms of wavelength, frequency and amplitude.
• We can feel electromagnetic waves release their energy when sunlight warms our skin.
• Remember that electromagnetic radiation can be described either as an oscillating wave or as a stream of particles, called photons, which also travel in a wave-like pattern.
• The notion of waves is often used to describe phenomena such as refraction or reflection whilst the particle analogy is used when dealing with phenomena such as diffraction and interference.

The visible spectrum is the range of wavelengths of the electromagnetic spectrum that correspond with all the different colours we see in the world.

• As light travels through the air it is invisible to our eyes.
• Human beings don’t see wavelengths of light, but they do see the spectral colours that correspond with each wavelength and colours produced when different wavelengths are combined.
• The visible spectrum includes all the spectral colours between red and violet and each is produced by a single wavelength.
• The visible spectrum is often divided into named colours, though any division of this kind is somewhat arbitrary.
• Traditional colours referred to in English include red, orange, yellow, green, blue, and violet.

The frequency of electromagnetic radiation (light) refers to the number of wave-cycles of an electromagnetic wave that pass a given point in a given amount of time.

• Frequency is measured in Hertz (Hz) and signifies the number of wave-cycles per second. Sub-units of Hertz enable measurements involving a higher count of wave-cycles within a single second.
• The frequency of electromagnetic radiation spans a broad range, from radio waves with low frequencies to gamma rays with high frequencies.
• The wavelength and frequency of light are closely linked. Specifically, as the wavelength becomes shorter, the frequency increases correspondingly.
• It is important not to confuse the frequency of a wave with the speed at which the wave travels or the distance it covers.
• The energy carried by a light wave intensifies as its oscillations increase in number and its wavelength shortens.