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VIBGYOR- A spectrum

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Visible Spectrum

Light is a form of electromagnetic radiation. It is composed of various wavelengths, each having its characteristics. VIBGYOR falls under the visible light region of the electromagnetic spectrum. It lies between the wavelength range of about $380 \ nm$ to $700 \ nm$. It has a frequency less than UV radiation and just greater than infrared radiation, as seen from the electromagnetic spectrum.


It is this visible light which enables vision. When light is reflected from a surface and reaches our eyes, we can see the object it was reflected from. It is also responsible for photosynthesis, transpiration, flowering, feeding habits, and many other related diurnal activities of plants and animals.


Splitting of White Light

White light is made of seven different colours, abbreviated as VIBGYOR. The VIBGYOR colours include- violet, indigo, blue, green, yellow, orange and red. Since frequency is constant irrespective, the wavelength for each VIBGYOR colour is directly proportional to speed. Therefore, the wave with a longer wavelength will have a higher speed. White light is made up of seven colours; each colour has a different wavelength. The colour with the longest wavelength is red; therefore, it has the lowest speed. Therefore, it shows the least bending during refraction. Whereas violet has the longest wavelength and, there, the fastest speed. It, therefore, refracts the most.


Due to differences in the speeds of each colour and thus different amounts of refraction, the white light splits into its seven constituent colours when refracted through a slab or prism. Therefore, through the prism, one can see the seven colours that constitute the white light as VIBGYOR.


Dispersion through a Prism Due to Different <a href='https://www.vedantu.com/maths/angles'>Angles</a> of Bending of Each Colour


Dispersion through a Prism Due to Different Angles of Bending of Each Colour


Characteristics of Each of VIBGYOR Colours

1. Wavelength

It is the distance between two crests or that between two troughs. The wavelength of various colours of VIBGYOR is


Colour

Wavelength (in nm)

Violet (V)

400-440

Indigo (I)

440-460

Blue (B)

460-500

Green (G)

500-570

Yellow (Y)

570-590

Orange (O)

590-620

Red (R)

620-720


2. Frequency

It refers to the number of waves passing through a point per second. The frequency of various colours of VIBGYOR is:


Colour

Frequency (in THz)

Violet (V)

668-789

Indigo (I)

600-700

Blue (B)

606-686

Green (G)

526-606

Yellow (Y)

508-526

Orange (O)

484-508

Red (R)

400-484


3. Photon Energy

Energy carried by a single photon of that colour, is called its photon energy. The photon energy of various colours of VIBGYOR is


Colour

Photon Energy (in eV)

Violet (V)

2.75-3.26

Indigo (I)

2.50-2.90

Blue (B)

2.50-2.75

Green (G)

2.17-2.50

Yellow (Y)

2.10-2.17

Orange (O)

2.00-2.10

Red (R)

1.65-2.00


Formation of Rainbow

Rainbow is a case of natural dispersion of sunlight (white light). It is formed after sunlight passes through raindrops, which act as a natural prism. Therefore, a rainbow can only be observed when we look opposite the sun’s direction, i.e., our back is towards the sun. When light strikes the water droplets, some of it is reflected, and the rest is refracted. This refracted light, when it enters our eyes enable us to see the rainbow. Each colour deviates by a different amount at a different angle; each colour is visible separately. The circular arc formed is due to reflection, whereas the splitting of colours is due to refraction. VIBGYOR represents the rainbow colours.


Rainbow Formation Due to Dispersion through Raindrops (Image of VIBGYOR Formation)


Rainbow Formation Due to Dispersion through Raindrops (Image of VIBGYOR Formation)


VIBGYOR and Colour Related phenomenon

The source of the white light we receive on Earth is the Sun. Depending on factors like the sun's position, the scattering of light is affected, and thus we see different phenomena. Some examples include-


1. The Sky is Blue in Colour.

The colour of the sky is due to the dispersion of light into seven colours and the scattering of these colours. The wavelength of blue light is smaller than red. This wavelength of blue colour is comparable to the size of particles in the atmosphere. Therefore, the scattering of blue light is better. This makes the sky appear blue.


2. The Sunrise and Sunset Appear Red

During the sunrise and sunset, the sun is just at the horizon. Due to this, light has to travel a longer distance to reach the Earth. As a consequence, blue light, which has a higher scattering tendency, scatters away before reaching the Earth. Therefore, by the time the light reaches the Earth, only red hues remain. The sunrise and sunset thus appear red.


Summary

in this article, we have discussed the splitting of white light into VIBGYOR colours. We also studied the characteristics of colours and the formation of a rainbow. The colour-related phenomenon will give us an insight into the various natural phenomena such as colour of the sky during the sunrise and sunset, and the blue colour of the sky.

Last updated date: 27th Sep 2023
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FAQs on VIBGYOR- A spectrum

1. How is refraction related to the splitting of white light?

Refraction is the bending of light at the interface/boundary separating two media. When light moves from a denser to a rarer medium, its speed increases, and it moves away from the normal. Whereas, when light moves from a rarer to a denser medium, its speed decreases, and it moves towards the normal. When light enters a prism, each colour separates out due to differences in speeds. Therefore, violet deviated the most and red the least.

2. Why is the water in the deep sea blue?

Sunlight is absorbed by water molecules, which scatter the many colours present in it. Longer wavelength colours can be easily absorbed. However, shorter wavelength colours will disperse. In the spectrum of white light, i.e. VIBGYOR, the blue hues have a short wavelength, whereas the red hues have a long wavelength. Therefore, the scattering of blue hues is greater, and thus the water in a sea appears to be blue.

3. During dispersion, which colour undergoes minimum deviation?

Dispersion of light is the phenomenon wherein white light splits into its seven constituent colours when passed through a prism. Dispersion takes place because each colour in white light has a different wavelength and, thus, a different speed after refraction. This also means that each colour is thus bent at a different angle, thus separating and spreading all the colours. The colour having maximum wavelength will have a maximum speed in a medium and thus a minimum refractive index. Therefore, it will show minimum deviation. Violet has a minimum wavelength and therefore shows maximum deviation, whereas red has a maximum wavelength and therefore shows minimum deviation.

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