Why does multiplying a wave's frequency by its wavelength give its speed?
An FM radio wave is about 3 m long. A wave of green light is about half a millionth of a meter long. Which one oscillates faster?
You could try to measure both. For electromagnetic waves there is a shortcut: one shared speed forces the answer.
In a vacuum, every electromagnetic wave travels at the same speed, the speed of light: c = 3.00 × 10⁸ m/s.
You have already used the wave equation v = fλ: a wave's speed equals its frequency times its wavelength.
For an electromagnetic wave in a vacuum, the speed v is always c.
So the wave equation becomes c = fλ, the same equation with the speed pinned at one value.
The left side never changes, so the right side cannot change either: frequency times wavelength gives 3.00 × 10⁸ m/s for every electromagnetic wave in a vacuum.
The two factors must trade: double the wavelength, and the frequency halves.
Radio waves have far longer wavelengths than visible light, so their frequencies are far lower.
The opening pair is settled without a measurement: the green light wave, with the far shorter wavelength, oscillates far faster.
An infrared wave has a longer wavelength than an ultraviolet wave. Which has the lower frequency?
Both travel at c in a vacuum.
At one shared speed, the longer wavelength must come with the lower frequency.
The infrared wave has the lower frequency.
One electromagnetic wave has twice the wavelength of another. How do their frequencies compare?
Both waves' frequency times wavelength must give the same c.
Twice the wavelength must be balanced by half the frequency.
The wave with twice the wavelength has half the frequency.
Of two electromagnetic waves in a vacuum, wave one has the longer wavelength. How do their frequencies compare?
Why must an electromagnetic wave with a longer wavelength have a lower frequency in a vacuum?
Wanda says: 'If one electromagnetic wave in a vacuum has a longer wavelength than another, it must have a lower frequency.' Is Wanda correct?
Two radio waves travel through a vacuum. The first has wavelength 2.0 m and frequency 1.5 × 10⁸ Hz. The second has wavelength 4.0 m. Enter the second wave's frequency, in Hz.
Microwaves have longer wavelengths than ultraviolet light. Which statement about their frequencies in a vacuum is correct?
One electromagnetic wave has 100 times the wavelength of another. Both travel through a vacuum. What is true of the first wave's frequency?