Colour of Sunlight

The colour of sunlight might seem yellow to our eyes, but in reality, it is actually white! And you may wonder after knowing that this white light is made up of seven different colours that combine, just like the colours you see in a rainbow. We already know that sunlight has different shades depending on how we see the world, bright mornings, colourful skies, and beautiful rainbows all exist because of it!

This article helps students understand the true colour of sunlight, how it splits into different colours through a simple experiment, and why the Sun sometimes appears yellow, orange, or even red. 

Table of Contents 

• Understanding Sunlight
• Demonstrating the Colour of Sunlight through an Activity
• Why Does the Sunlight Appear Red, Orange, or Yellow?

Understanding Sunlight

Sunlight is the natural light that comes directly from the Sun. It travels as electromagnetic waves, and the part we can see is in the form of visible light.

When someone asks, “What is the colour of the Sun?”, most people quickly answer yellow or white. Some may even say red or orange, thinking of dawn and dusk. But surprisingly, all these answers are incorrect!

In reality, Sunlight is actually made up of seven different colours, including violet, indigo, blue, green, yellow, orange, and red. 

We often learn that the Sun is a “hot red ball,” but its true colour is white because it emits all the colours of visible light together. It is only due to Earth’s atmosphere that the Sun appears yellow, orange, or red at different times of the day.

We already know, when sunlight reaches Earth, it helps plants grow, lights up our surroundings, and makes it possible for us to see colours. Without sunlight, life on Earth would not exist!

But how exactly does sunlight consist of a mixture of seven different colours?

Wondering if this is really true? Yes, it is! And the best part is, we can prove it by a simple activity.

Demonstrating the colour of Sunlight through an Activity

To perform this activity, we require a glass prism and, white sheet of paper. Next, let's discuss the steps needed to follow this activity. 

• Take a glass prism and go to a slightly darkened room.
• Position the prism in such a way that direct sunlight enters the room through a small hole in the window shutter and falls on the prism.
• Fix the white sheet of paper on the opposite wall where the refracted sunlight from the prism will fall.
• Observe the pattern formed on the paper carefully.

Here, you will notice that the sunlight splits into a beautiful spectrum of colours, just like a rainbow! Interesting, isn't it? 

All seven colours, i.e Violet, Indigo, Blue, Green, Yellow, Orange, and Red, will be on a paper sheet. 

From this, it can be concluded, 

“Sunlight is a mixture of seven colours. When these colours combine, they form white light, which is what we normally see as sunlight.”

Now that we know sunlight is a mixture of different colours, another question arises: why don’t we see sunlight directly as seven colours? 

Even though sunlight is made up of seven colours, we do not see them separately when we look at the Sun directly. What is the reason behind this?

This happens because of the way sunlight interacts with Earth’s atmosphere. Let’s understand how this works.

When the Sunlight enters the atmosphere of Earth, it gets affected by airmolecules, dust, smoke, and pollution. These tiny particles scatter the light in different directions. We already know that each colour in the spectrum has a different wavelength:

• Blue and violet, which have shorter wavelengths, are scattered the most.
• Colours with longer wavelengths, like red and orange, scatter much less.

Because all these colours are scattered in different amounts and mix back together, our eyes see the sunlight as white, not as a spectrum of seven colours.

Why Does the Sunlight Appear Red, Orange, or Yellow?

Have you ever wondered why the Sun looks bright yellow at noon but turns orange or deep red during sunrise and sunset? The colour of sunlight changes because of the way it travels through the atmosphere of Earth at different times of the day. Let’s discuss how exactly it happens!

• Sunlight at Noon

At noon, the Sun is directly overhead, and sunlight travels the shortest distance through the atmosphere. This affects how the colour of the sun appears to us.

➔ Only a small amount of scattering of light happens.
➔ Blue light scatters the most, which makes the sky look blue.
➔ The light that finally reaches our eyes appears yellowish, making sunlight look bright white-yellow during noon.

• Sunlight in the Morning and Evening 

During sunrise and sunset, sunlight travels a much longer path through the atmosphere of Earth, which changes its colour dramatically.

➔ The Sun is close to the horizon, so the light must pass through more air, dust, and particles.
➔ More scattering happens, removing most of the blue and even some yellow light.
➔ Only the longer wavelengths, which are orange and red, reach our eyes.

This is why sunlight appears orange or red during dawn and dusk, creating the beautiful sky colours we often see. 

Till now, we have seen that the colour of sunlight may appear different throughout the day, but in reality, it is pure white light made of seven colours. From creating rainbows to painting the sky orange and red, sunlight plays an important role in how we see the world.