🔍 Frequency - the number of crests that move past a certain point in a given time, measured in Hertz
📝What is dispersion?
Dispersion is the separation of white light into the seven (7) different colours of the visible light spectrum. This occurs when white light is shone through a prism.
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📝What are the colours of the visible light spectrum?
The seven colours are the following:
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The seven colours are sometimes referred to as ROY G BIV
Red has the lowest frequency and as we progress up from there, the frequencies increase. The 7 colours are refracted at different angles due to their differing wavelengths, resulting in the visible rainbow.
Refraction occurs when a light ray passes through a medium that has a different density, e.g. air to glass. If the medium is denser, the ray of light will bend towards the normal. As it reemerges or enters a medium that is less dense, the ray of light will bend away from the normal. The prism, a denser medium than air, causes the ray of white light to refract and separate into the different coloured rays of light it is comprised of, resulting in the visible light spectrum.
📝What is UV and infrared?
UV, also known as ultraviolet, is a higher frequency than violet, hence the name. Infrared is on the opposite side of the spectrum, being a lower frequency than red. Both of these waves are invisible and don't give off a colour.
Infrared was first discovered by William Herschel in 1800. William Herschel was well known as a musician as well as an astronomer. The original experiment that led to the discovery of infrared was centered around how much heat was passed through the different coloured filters that Herschel used to observe the sun. Through this experiment, he concluded that the temperature increased, the lowest being violet and the highest being red. After noticing this pattern, he decided to measure just outside of the red where there was no visible sunlight (colours) and found that the temperature just beyond the red was higher than the temperature measured in red.
After infrared was discovered, UV was discovered by Johann Wilhelm Ritter in 1801. Johann Wilhelm Ritter was a German chemist and physicist and was inspired by Herschel's discovery of an invisible light beyond the red portion of the spectrum. While attending the University of Jena, Ritter conducted an experiment using silver chloride, a compound that turns black when exposed to sunlight. He placed this chemical compound just beyond the violet portion of the spectrum and noticed that it reacted faster than it did when placed in the violet portion.
