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Sunlight is the key factor responsible for life on earth. Sunlight is also synonymous with terms such as “solar radiation” or “sunshine”. The Sun is the only star in the solar system in which we live. It emits electromagnetic radiation. The components of electromagnetic radiation from sunlight have different wavelengths. Out of all the electromagnetic waves, only visible light is detectable to the human eyes.
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Key Takeaways: Sunlight, Colour of sunlight, Sun, VIBGYOR, Dispersion, Rainbow, Scattering, Prism
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What is the Colour of Sunlight?
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Sunlight appears as white colour to human eyes, but actually, it consists of a band of seven different colours mixed together in sequence.
VIBGYOR is the acronym given to this band of seven different colours in the white sunlight. Sunlight consists of the following seven colours:
- V – Violet
- I – Indigo
- B – Blue
- G – Green
- Y – Yellow
- O – Orange
- R- Red
This can be understood with the help of a glass prism. When a single beam of sunlight passes through a glass prism, the white sunlight splits into seven different colours.
Splitting up of white light (or sunlight) into seven different colours on passing through a transparent medium, like a prism or water droplet, is called dispersion. This phenomenon proves that the sunlight which appears white to human eyes is actually made up of seven different colours.
Read More: Electromagnetic spectrum
Different colour of sunlight at different time of day
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Colour of Sunlight at different times in a day are as follows:
Noon
When the sun is high overhead in the sky, the rays travel less distance and for a lesser period in the earth’s atmosphere, so the sun rays suffer the least amount of interference and are thereby less scattered. Blue light is scattered more than other colours (other colour lights are scattered even less in this least interference) because it has shorter, smaller waves. Consequently, the blue light is scattered throughout the sky and the sky appears blue whereas the colour of sunlight appears yellow.
Morning and Evening
During the dawn and dusk, the sun is near the horizon due to which the light rays have to travel a longer distance and for a longer period of time through the earth’s atmosphere. This results in more interference, which thereby causes more scattering of light. Ultimately, most of the colours, including blue and yellow, are scattered leaving the red light. Hence, the colour of sunlight appears in the range of orange and red during sunrise and sunset.
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Why are seven colours in Sunlight are important?
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It is because of these colours we are able to see different things. If sun rays didn’t consist of colours, everything would appear of the same colour. An object (leaves) appears green to us because it reflects the green coloured light and absorbs all other colours. If an object would absorb all the colours, it would appear black to us.
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Points to Remember
Following are some important points:
- Light rays from the Sun take approximately 8.3 minutes to reach our Earth.
- Sunlight is the main source of energy behind the mechanism of photosynthesis.
- Every place on Earth doesn’t receive the same amount of sunlight in a given period. While some places in the equatorial region receive evidently more sunlight than places near Earth’s poles.
- Sunlight produces Vitamin D in our bodies. But on the side effect, ultraviolet rays are also mutagen.
- In the 1660s, Sir Isaac Newton, who performed experiments with sunlight and prisms discovered that white light was composed of many different colours.
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Sample Questions
Ques: How does a rainbow form? (2 Marks)
Ans: Rainbow formation is a natural phenomenon. Rainbow is usually seen when rain is immediately followed by a bright sun in the sky. The phenomenon of dispersion of light is the reason behind the formation of the rainbow. Raindrops that are suspended in the atmosphere act like a prism and disperse the sunlight. This leads to the scattering of white sunlight into seven different colours, thus forming a rainbow.
Ques: Why don’t we see sunlight as seven colours? (2 Marks)
Ans: Sunlight is made up of seven colours; Violet, Indigo, Blue, Green, Yellow, Orange, Red; but we don’t see sunlight as seven colours. When the sun rays enter the earth’s atmosphere, it gets distorted by air molecules, water vapour, dust, smoke and pollutants in air. As different colours of the spectrum have different wavelengths, different colours are distorted to varying extent. The short-wavelength blue and violet light are scattered more than colours of high wavelength. So, we don’t see sunlight as seven different colours.
Ques: What is the colour of the Sun when seen from space? (2 Marks)
Ans: When the sun rays enter the earth’s atmosphere, it gets distorted by air molecules, water vapour, dust, smoke and pollutants in the air. As different colours of the spectrum have different wavelengths, different colours are distorted to varying extents. But in space we don’t have air molecules, water vapour, dust, smoke and pollutants, sunlight is not distorted. So, from space, like from the International Space Station, the sun will appear like a white glowing sphere.
Ques: Why does the sun appear yellow? (2 Marks)
Ans: The sun appears yellow to us because of the Earth’s atmosphere. When sunlight hits atmospheric particles, it redirects the sun rays in all directions. This process of redirecting sunlight to all directions is called scattering. The Earth’s atmosphere scatters away blue, indigo and violet light more, while colours like red, orange and yellow are scattered less. Due to this unequal scattering, the sun appears yellow to us.
Ques: Short note on Sun. (2 Marks)
Ans: Sun is the only star in our solar system. The sun contains massive quantities of helium and hydrogen, and generates huge amounts of energy, in the form of light and heat energy due to reactions called nuclear fusion. Due to this huge energy the surface temperature reaches around 5600?. Though the mass of the sun can be measured directly. Indirectly the Sun’s mass is found to be about 1.989 × 10 30 kg.
Ques: What are convex and concave mirrors? (2 Marks)
Ans: Convex mirror: It has a convex reflecting surface. Concave mirror: The reflecting surface of this is concave. Convex mirror is also known as a diverging mirror because it diverges the light, whereas a concave mirror is also known as a converging mirror because it converges the light. Convex mirrors are used as rear-view mirrors in cars, security mirrors in public places, etc. On the other hand, concave mirrors are used as a cosmetic mirror, in torches, automobile and searchlights, doctor's head mirrors, solar furnaces, etc.
Ques: What is the electromagnetic spectrum? (2 Marks)
Ans: The electromagnetic spectrum is a range of frequencies, wavelengths and photon energies. The frequencies range from below 1 hertz to above 1025 Hz and the wavelengths range from a few kilometres to nanometres. Generally, in vacuum electromagnetic waves tend to travel at the speed of light.
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