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Wavelength of Light

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Last updated date: 16th Jul 2024
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Wavelength of Light - Relationship Between Frequency and Wavelength

Light is the electromagnetic radiation that occurs within a specific section of the electromagnetic spectrum. The term essentially refers to the visible light, it is the light that is distinguishable and visible to naked human eye and it is also responsible for the sense of light. The wavelengths of the visible light range between 400-700 nanometers, this is between the infrared having longer wavelengths and the ultraviolet having shorter wavelengths. 

The wavelength of the visible light indicates that its frequency is approximately 430-750 terahertz (THz). The light speed in the vacuum is 299,792,458 metres per second as per the experiment. The visible light like other forms of the electromagnetic radiation moves at this speed specifically in the vacuum. In physics, the definition of light often refers to the electromagnetic radiation having any wavelength, regardless of if it’s visible or not. The forms of radiation such as radio waves, gamma rays, microwaves, and X-rays are all different forms of the light. 

The light exhibits both particle nature and wave nature and the occurrence of this phenomenon is described as light's dual nature. Light exists in the form of particles and propagates in the form of wave. The study associated with light is called optics, and optics is an important domain in the study of physics. 

Light doesn’t necessarily travel in the straight line but it travels in transverse waves. The wave that is made of oscillation when moving and that occurs perpendicular to direction of energy transfer is known as the transverse waves. Wavelength is essentially the distance between two consecutive troughs or two consecutive crests in the transverse wave. The wavelength is also used for representing repeating pattern of travelling energies, like sound or light.

Wavelength:

We know that light can be understood both as a particle and a wave. Photons are the light particles which exist in the form of "packets" of electromagnetic energy. On the other hand, waves are the form of energy where electromagnetic radiation takes on when it is propagating.

Light does not travel in a straight light line. It travels in the form of a transverse wave. A wave which consists of oscillation while moving which occurs perpendicular to the direction of transfer of energy is called transverse waves. Wavelength is the distance between two consecutive crests or two consecutive troughs in a transverse wave. Wavelength also represents a repeating pattern of any traveling energies, such as light or sound. Wavelength is usually expressed by the units of nanometres (nm) or micrometres (µm). It is represented by the symbol λ which is read as lambda.

The frequency and Wavelength Relationship

The frequency and wavelength are closely associated with each other, especially in relation to light. Wavelength is the distance between two consecutive troughs or crests whereas frequency is defined by the number of waves which pass via a single given point within the specified period of time. The wavelength and frequency are inversely proportional which means the longer the wavelength, the lower is the frequency. The frequency tends to be higher when specifically the wavelength is short since more troughs and crests pass via the specific point when wavelength tends to be short. Conversely the frequency tends to be lower when wavelength exhibits a longer path.

Table of the Wavelengths of Various Colours, and Their Frequencies:

Colour

Wavelength in nm

Frequency in THz

Red

750 - 610

480 - 405

Orange

610 - 590

510 - 480

Yellow

590 - 570

530 - 510

Green

570 - 500

580 - 530

Blue

500 - 450

670 - 600

Indigo

450 - 425

600 - 700

Violet

425 - 400

700 - 790

White Light: White light's wavelength extends from 400 to 750 nm. When the white colour is passed through the prism, the light spectrum is formed due refraction of different wavelengths through different angles.

Ultraviolet Light: Ultraviolet light extends from the end of the visible region and the X-ray region in the electromagnetic spectrum. It gets its name as it is the light closest to the violet portion of the visible light and is in the range of 10 to 400 nm.

Infrared Light: Infrared radiation has a longer wavelength than visible light and is close to the red portion of the visible spectrum of light. It extends from 750 nm to 1 mm. Infrared radiation cannot be seen but can be felt in the form of heat.

Red Light and Orange Light: Red light and orange lights whose wavelength lies between 750 to 610 nm and 610 to 590 nm respectively are best viewed naturally during sunrise and sunset. This is because the associated wavelengths of red and orange from sunlight are not properly scattered by the atmosphere during these times.

Yellow Light: Yellow light has a wavelength between 590 and 570 nm. Yellow light is emitted by low-pressure sodium lamps.

Green Light: Green colour, whose wavelength extends from 570 to 500 nm, can be prominently seen in grass and leaves. Grass reflects green wavelength and absorbs all other wavelengths and thus appears green.

Blue Light: Blue light has a wavelength ranging from 500 to 450 nm. The atmosphere scatters shorter wavelengths efficiently and thus the wavelength corresponding to the colour blue is scattered efficiently by the atmosphere. That’s why the sky appears blue when we look up at it.

Indigo Light Violet Light: With a wavelength between 450 and 425 nm, indigo is a colour which is between the primary colour blue and the colour violet in the colour wheel. Violet with a wavelength of 425 to 400 nm is the visible light with the shortest wavelength. It has a shorter wavelength and is hence scattered more effectively by the atmosphere. But since our eyes are sensitive to blue colour, the sky appears blue rather than indigo or violet colour.

FAQs on Wavelength of Light

1. What is the wavelength of light mainly dependent on?

The wavelength of light mainly depends on two factors: the propagation speed and frequency. The wavelength is inversely proportional to frequency and directly proportional to propagation speed. The higher propagation speed means lower translates longer wavelength while the opposite is true in case of frequency and wavelength since they are inversely proportional to each other. The lower the frequency, the longer is the wavelength and vice versa.

2. What is the wavelength range of different colored light?

The different colour lights have different ranges of wavelength in nm. The red colour has the wavelength range of 750-610 nm, the orange light has wavelength in the range of 610-590 nm, the yellow light has wavelength in the range of 590-570 nm. Similarly the green light has a wavelength range of 570-500 nm, blue light 500-450 nm, Indigo 450-425 nm, and the violet light has the wavelength in the range of 425-400.

3. What is the frequency range of different colored light?

The frequency of the light is measured in THz. The frequency of red colour is in the range of 480-405 THz, the frequency of orange has a range of 510-480, and yellow has a frequency range of 530-510 THz. Similarly green colour has a frequency range of 580-530 THz, blue has the frequency range of 670-600, the frequency range of Indigo is 600-700 THz, and the Violet colour has the frequency range of 700-790 THz.

4. What is the concept of different colored lights that are visible to the human eye?

The light is made using various wavelengths and each of the wavelengths generally corresponds to the different colour. The colour that you see is caused by wavelengths getting reflected from the object that you are viewing. The visible spectrum defines a spectrum of light that is distinguishable and visible to naked eye. This spectrum ranges between dark red which is 700 nm to the violet which is at 400 nm.

5. How can I learn about light wavelength in more detail?

If you want a detailed documentation of the wavelength of light for helping you prepare for the physics exam then the notes provided by Vedantu are extremely reliable. Vedantu is a leading learning platform with a wide array of learning resources that can be downloaded for free. The chapter on wavelength of light provided by the Vedantu app or website can be downloaded in the PDF file for free on your device.