Wavelength is a basic concept in optics. Here you can learn more about wavelengths.
Electromagnetic radiation is considered a combination of alternating electric fields and magnetic fields that travel through space with a wave motion. Because radiation acts as a wave, it can be classified in terms of wavelength and frequency.
Wavelength is the distance between two points of the same phase on a periodic wave (Fig.1).
Fig.1 Wavelength definition.
Frequency refers to the number of occurrences of a periodic event and is measured in cycles per second. The frequency of a wave tells us the number of waves that pass a certain point in a specified amount of time.
The wavelength is inversely proportional to the frequency of the wave, which means that a wave with a long wavelength has a low frequency and a wave with a short wavelength has a high frequency. Additionally, the waves with the shortest wavelengths have the highest amount of energy.
The wide range of electromagnetic waves, creates an electromagnetic spectrum.