Electromagnetic Spectrum GCSE Explained.
The electromagnetic spectrum is the range of frequencies or wavelengths of radiation that consists of Waves that propagate through space without a need for a medium to travel through. This means that they are able to travel through a vacuum which is good since most of the universe is actually a vacuum. The wavelengths range from extremely long radio waves, through shorter microwaves, then infrared waves before moving into the visible spectrum which our eyes can detect. The visible spectrum is a narrow band of light between approximately 380 and 700 nanometres, which follows the well-known pattern explained by the mnemonic ROYGBIV. The first wavelengths are longest and the last are shortest going from red, orange, yellow, green, blue, indigo and violet. Following the visible, the next shortest part of the spectrum is ultraviolet light, followed by x rays and finally gamma rays. These last portions of the electromagnetic spectrum have large amounts of energy due to their high frequency which makes them potentially dangerous.
What is the Longest Wavelength?
Radio waves are by far the longest wavelength since they are by definition the longest. There is no theoretical limit to how long these waves are and they could be infinitely long in theory. There is probably a limit to how long wavelengths can get however as the universe stretches out em waves over time, known as redshifting, but the universe is has had a finite existence, so far. Red light is the longest wavelength of the visible part of the spectrum, as evidenced by the rainbows that have red on their outermost edge after white light has been split.
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