Our sun is 149.6 million km away from us and It takes 8 minutes 20 seconds for sun rays to reach the earth. Now let’s begin
How will you react if I suddenly ask you “WHAT IS THE COLOUR OF THE SUN”?
Almost 60 – 70% people in my case say it’s yellow or orange, but what if i say you are totally wrong. If I tell you that the color of the Sun is white, would you believe it or not?
But it’s true, the colour of the sun is white. If we see the Sun from space, then we see it in white color. But if we see the Sun from the Earth, then we see it in yellow or red color. But why does it happen that the sun rays appears yellow to us from the earth?
So let’s start to know the reason behind this.
Why does the sun rays look yellow from the earth?
As I told you before, sun and sunrays are white in color. This is because of the temperature of the sun which is 5500°C and the stars of this temperature are visible only by white color. Stars below 5000℃ appear orange because they are comparatively cold and the stars with temperatures above 6500 ℃ appear blue due to being hot.
Now as we know the sun appears red at sunrise. But why is it happen whereas in reality it is white.
So You all must have learn about desperssion of light in you classes. In this we have learnt that white light is separated into its component colours – red, orange yellow, green, blue, indigo and violet. We can see these colors together in the rainbow itself.
Rays of smaller wavelength, which do not cover much distance like violet, blue and indigo, after colliding with dust, particles and gas, they spread in the atmosphere. But larger wavelength rays i.e. which can cover more distance such as yellow red and orange, it does not spread much in the atmosphere and it is directly visible to our eyes by the sun.
That is, when the sun is near the horizen, the thick layer of the atmosphere filters the color of the sun and makes it look red. Now as the sun rises, that is, in the afternoon, the sun’s rays have to travel a short distance, due to which the layer of air in the atmosphere also decreases. And this is the reason when we try to see the sun in the afternoon, we see it in its true color (means in white colour). As we go to the height, the air layer will decrease and hence the sun will appear more white as compared to ground. But one more question which is also very interesting that is how rainbow form?
What is refraction?
Refraction is the bending of light when it travels from one medium to another.
Why do we see rainbow?
As we all know that when a light passes through prism, it is divided into seven colors. You must have noticed that rainbow is formed mostly during the rainy season.
The same concept also applies in rainbow when it is formed. So when the sun rays passes through the raindrops, it divides into seven colors (when sunlight is refracted by water droplets in the atmosphere).
But also there is a condition that we will see the rainbow only when the sun is behind us and the rain has come ahead of us.
Hence when a sunlight enters the water droplet during the rain, it enters as a single beam of light but due to change in medium (air to water ) all the colours bend at different angle and giving us amazing bend of colours which is called spectrum.
Why rainbow is formed in the shape of arc?
Those seven colors of Rainbow, we know by the common name VIBGYOR. So rainbow is formed in the shape of arc due to internal reflection. But the question is “is the rainbow actually curved”? If it is, then why it is formed in a semicircle and not in any other shape or curve?
Each color in a rainbow have different wavelength, so due to this all the colour light bend differently means they refract differently. For example : very low wavelength coloured light such as violet(380 – 450 nm) refracts the most and the maximum wavelength light such as red(620 – 750 nm) refracts the least.
So when the sunlight touches the surface of the second medium, all of them internally reflect back and they reflect back at an approximate angle of 42° and when this coloured light actually come out the rain drop after the internal reflection and then we see the rainbow. It mean all the rainbow lights(reflected lights) falls in your eyes at an angle 42° then the spectrum of light will be formed in the shape of semicircle. but still the question is why it happens at 42°?
Any light that is coming from outside this particular rainbow will be making an angle of 42° but it is not falling in my eyes and for me to see anything, light must be falling in my eyes. The same thing for all the colour lights which is coming from below the rainbow as well, Which is hitting at 42° on my body and not coming into my eyes so again I am not able to see it, So a rainbow might actually not be a rainbow, It is a plane of colours but due to this 42° angle and light falling into my eyes, It gives me a shape of a curve but not any semicircle it’s a complete circle. But if it is a complete circle then why you see it as a Semicircle?
It is because of the horizon.
But if you are on a flight and look into the sky during the rain you might be able to see a complete rainbow.