Seven Colors in a Rainbow and absent colors

People have a joy in seeing Rainbow in the fresh sky after a rainstorm. It looks very pleasing to our eyes. I use to find rainbow in the sky every time after the rainfall. But, what causes a Rainbow? Do you know that? I read in Physics book that a Rainbow has seven different colors. But, I can see only four or five of these. You might have noticed the same thing like me. Have you ever wondered why we don’t see all seven colors in a Rainbow? Again, what about the other colors than these seven? Well, I am here to disclose it!

Table of Contents:

  1. Causes of a Rainbow
  2. Conditions of Rainbow formation
  3. List of Seven colors in a Rainbow
  4. Absence of Colors in the Rainbow
  5. Why we don’t see all seven colors in a Rainbow?

What Causes a Rainbow?

Image of Rainbow
Image of a Rainbow

Dispersion, refraction and total internal reflection of light are three physical phenomena that help to form a Rainbow. Dispersion of light is the main cause of a Rainbow and other two phenomena assist it. Here I am going to explain the formation of Rainbow in a simple way.

After the rain, the sky becomes very fresh and clear. So many water droplets float in the air at that time. When sunlight falls on the droplets, the light enters inside the rain drops and breaks into the seven different colors by the phenomenon of dispersion. Then a bunch of light rays of seven colors reflects parallelly in a band-like region with their entire intensity. This phenomena of reflection of light within a band-like region with no loss in intensity is known as total internal reflection of light. Now, instead of white sunlight, this band of light of seven colors which is known as Rainbow, becomes visible to our eyes.

Why don’t we see Rainbows all the time? – Conditions of Rainbow!

We cannot see Rainbow at all the time. Actually, a Rainbow forms under some conditions. Here I have listed all possible conditions for Rainbow formation.

  • You can see rainbow after the rain. Because enough moisture in the sky is essential for rainbow formation.
  • Sky should be clear and the Sun must be closer to horizon. Because, the light must fall on the droplets with an angle below 42 with respect to horizontal. This is why the rainbow is seen mostly at the afternoon.
  • The position of Sun must be behind you.

All these conditions do not satisfy all the time. Therefore, we don’t see rainbows all the time.

List of Seven colors in a Rainbow

We know that there are seven colors of a rainbow. Can you remember all these colors? If No, then check the list of seven colors of a rainbow at below.

  1. Violet
  2. Blue
  3. Indigo
  4. Green
  5. Yellow
  6. Orange
  7. Red

Absence of Colors in the Rainbow

Out of these seven colors only four or five are visible in rainbows. Which colors are absent and which are visible? If you observe the rainbow carefully, you will be able to see Red, Yellow, Green and Blue rays only and other rays cannot be seen with naked eyes. But, there are other some colors like Pink, Brown, Black, Peacock green, Purple, etc. which are not even exist in a Rainbow.

Why don’t see all colors in a Rainbow?

Rainbow over a river
Only four colors are visible in Rainbows

Now, I have two questions to answer. Why don’t we see all seven colors in the rainbow and why some colors like brown, pink are not present in a rainbow?

I will prefer to answer the second question first. By the process of dispersion, the white light breaks into the seven spectral colors of visible spectrum which have their own wavelengths. Other colors like Pink, Brown, Purple, etc. are not the spectral colors. These colors do not have their own wavelengths.

On the other hand, we can see only four or five spectral colors in a rainbow when we see it with naked eyes. This is because these four five colors are more responsive to our eyes. Other colors cannot produce a clear visual sensation to our eyes. However, all the colors can be seen if we seen the rainbow with a telescope.

Can we make Rainbows artificially?

Of course! You can form a rainbow by own. You need to place a water-filled spray bottle at a place where the enough sunlight falls. Keep the Sun behind you and bottle. That’s it. Then wait for some times to see your own rainbow.

Hope you understand how many colors are there in a rainbow and why don’t we see all seven colors in rainbows. This is all from this article. If you still have any doubt on this topic you can ask me in the comment section. Keep visiting this website for more interesting articles of Physics.

Thank you!

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