Main Properties of Waves
There are three main properties of a wave: its velocity, wavelength, and frequency.
- Wave velocity (v) — how fast a wave propagates in a given medium. Its unit is meter per second (m/s). In a vacuum, light travels at approximately 299,792,458 m/s.
- Wavelength (λ) — the distance over which the shape of a wave repeats. It depends on the medium in which a wave travels. It is measured in meters (m).
- Frequency (f) — how many times per second the particles of a medium vibrate when the wave passes through it. The unit of frequency is Hertz (Hz), equivalent to 1/second.
Wavelength Formula
The relationship between wavelength, wave speed, and frequency is described by this simple equation:
λ = v / f
Where:
- λ (lambda) = wavelength in meters (m)
- v = wave speed in meters per second (m/s)
- f = frequency in Hertz (Hz)
You can rearrange this formula to solve for any of the three variables:
- Wavelength: λ = v / f
- Frequency: f = v / λ
- Wave Speed: v = λ × f
How to Calculate Wavelength
- Determine the frequency of the wave. For example, f = 10 MHz. This frequency belongs to the radio waves spectrum.
- Choose the velocity of the wave. As a default, our calculator uses the speed of light in a vacuum: 299,792,458 m/s.
- Substitute these values into the wavelength equation λ = v / f.
- Calculate the result. In this example: λ = 299,792,458 / 10,000,000 ≈ 29.98 m.
You can also use this tool as a frequency calculator — type in wave speed and wavelength to find the frequency. Or calculate the wave speed from frequency and wavelength.
Typical Wave Speeds
| Medium | Speed (m/s) | Speed (ft/s) |
|---|---|---|
| Light in vacuum | 299,792,458 | 983,571,056 |
| Light in water | 224,901,000 | 737,862,861 |
| Sound in air (20 °C) | 343.2 | 1,125.3 |
| Sound in water (20 °C) | 1,481 | 4,859.6 |
The Electromagnetic Spectrum
The calculator automatically identifies the type of electromagnetic wave based on the calculated wavelength:
| Type | Wavelength range |
|---|---|
| Radio waves | > 1 m |
| Microwaves | 1 mm – 1 m |
| Infrared (IR) | 750 nm – 1 mm |
| Visible light (red) | 620 – 750 nm |
| Visible light (orange) | 590 – 620 nm |
| Visible light (yellow) | 570 – 590 nm |
| Visible light (green) | 495 – 570 nm |
| Visible light (blue) | 450 – 495 nm |
| Visible light (violet) | 380 – 450 nm |
| Ultraviolet (UV) | 10 nm – 380 nm |
| X-rays | 0.01 nm – 10 nm |
| Gamma rays | < 0.01 nm |
FAQs
How does light wavelength affect photosynthesis?
The best wavelengths of light for photosynthesis are blue (375–460 nm) and red (550–700 nm). These wavelengths are absorbed as they have the right amount of energy to excite electrons in the plant's pigments — the first step in photosynthesis. This is why plants appear green: the red and blue light that hits them is absorbed, while green light is reflected!
Does frequency change when a wave passes from one medium to another?
No — frequency does not change when a wave moves between media. However, wave speed (and therefore wavelength) does change. Use the wavelength formula with the same frequency but a different wave speed to find the new wavelength in the new medium.
What is the wavelength of red light in water?
Red light in air has a wavelength of approximately 700 nm and travels at 299,792,458 m/s. In water, light slows to about 224,901,000 m/s. Using f = v/λ (frequency stays constant), the wavelength in water becomes approximately 700 × (224,901,000 / 299,792,458) ≈ 525 nm.
What are metric and imperial units for wavelength?
- Metric: picometers (pm), nanometers (nm), micrometers (μm), millimeters (mm), centimeters (cm), meters (m), kilometers (km)
- Imperial: inches (in), feet (ft), yards (yd), miles (mi)