Brainlag PlusThe seven groups in order, what they share, c = fλ in standard form, and timing radar echoes and satellite signals.
One family, seven groups
Electromagnetic (EM) waves are transverse waves that transfer energy from a source to an absorber.
Light is one of them; it just happens to be the band our eyes detect.
In order of increasing frequency (and so decreasing wavelength):
- Radio waves (wavelengths from about a millimetre to kilometres)
- Microwaves (around a centimetre)
- Infrared
- Visible light (400 nm violet to 700 nm red)
- Ultraviolet
- X-rays
- Gamma rays (smaller than an atom)
The spectrum is continuous: the groups merge into each other. Make up your own memory sentence from the first letters R, M, I, V, U, X, G; one you invent sticks better than one you are given.
Every EM wave travels at the same speed in a vacuum, 3.00 × 10⁸ m/s, and almost as fast in air. Papers give you this value.
The rest of this lesson and its 12 practice questions are in Plus.
Screen 1 of 4, free to read.
- 12 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards