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Wavelength of Light


The wavelength is nothing but the length of a wave. The wavelength of light will be so small that it is expressed in nanometers (nm). In the modern physics its accepted that the light has a dual nature. Sometimes it acts as mass less particles and the other times as waves. If light is taken as a wave, the visible light has several colors having its own wavelength slightly varying from other that determines other properties of the light wave like frequency, speed etc.
Waveform Showing Wavelength
Wavelength of a wave.

Wavelength of Light Formula

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The light wave has its own frequency, wavelength and speed. To calculate the wavelength of light, use formula
$\lambda$ = $\frac{c}{f}$

Since the speed of light is constant (c = 3 $\times$ 108 m/s).
Hence, the formula is

$\lambda$ = $\frac{3 \times 10^8\ m/s}{f}$where f is the frequency of light.

The frequency varies from violet to red. Hence the wavelength varies depending on its frequency.

Wavelength of Visible Light

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The visible spectrum of light comprises of following colors: Violet, Indigo, Blue, Green, Yellow, Orange, Red has known as VIBGYOR. It corresponds to the wavelength range of 400-700 nm. It varies from shortest to longest wavelength. The white light is composed of all these colors present in the visible spectrum.

Visible Light Spectrum

Light Color
Violet 390 - 420
Indigo 420 - 455
Blue 455 - 492
Green 492 - 577
Yellow 577 - 597
Orange 597 - 622
Red 622 - 780

How to calculate wavelength of light?

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Lets see some examples on how to calculate the wavelength of light:

Solved Examples

Question 1: A light wave has frequency of 6.23 $\times$ $10^{14}$ Hz. Calculate its wavelength and determine in which color it lies in the spectrum.
Frequency of wave = 6.23 $\times$ $10^{14}$ Hz

The wavelength of light wave is given by,
Wavelength $\lambda$ = $\frac{3 \times 10^8\ m/s}{6.23 \times 10^14}$
                    = 481 nm

Question 2: Calculate the frequency if the wavelength of wave is 660 nm.
Wavelength of wave $\lambda$ = 660 nm

The frequency of light wave is given by,
Frequency f = $\frac{3 \times 10^8\ m/s}{\lambda}$
                  = $\frac{3 \times 10^8\ m/s}{660 \times 10^-9\ m}$
                  = 4.5 $\times$ $10^{14}$ Hz.