Blue colour of the sky, and Tyndall effect

The blue sky is one of the most commonly seen sights on Earth. It is generally defined as the sky in the daytime that appears blue because of Rayleigh scattering.   The blue colour of the sky is also referred to as cyan, azure, cerulean, and navy. The blue colour of the sky varies from moderate blue to navy blue and sometimes even to midnight blue. The blue sky is typically seen in the tropics and subtropics.

Blue colour of the sky:

The colour of the sky can tell us a lot about the weather and the time of day. The blue colour of the sky is caused by Rayleigh’s scattering, which is when light is scattered as it passes through the atmosphere. The blue colour of the sky is most visible in the late afternoons and early evenings. It is because the light from the sun is scattered more by the atmosphere during these times.

What colour is the sky?

There are several different colours of the sky. However, blue is the most commonly observed and seen colour on Earth. The different colours of the sky are caused by the combination of light being scattered by different air molecules, which change the colour of the scattered light. This phenomenon is often referred to as the ‘colour of the sky’ or the ‘sky colour’ and can vary from one location to another. The colour of the sky is determined by the altitude of the Sun above the horizon, the time of day, the weather conditions and the presence of pollution in the atmosphere.

Blue: The colour of Daylight

We see blue because spectra study the colour of light, and the scattered blue light from the Sun is what we see when we look at the sky. The blue colour of the sky is also known as the colour of daylight or illuminance, and it is measured in units of light intensity per unit area, often called lumens. The amount of light that reaches Earth’s surface is called luminance, and it is measured in lumens per square metre (lm/m2). The brighter the light, the higher the lumens per square metre.

Atmospheric Refraction:

On a clear day, you can see for miles in every direction, and the blue colour of the sky is the result of the mixture of light from the Sun which has passed through the air and the white light which has bounced off the atmosphere – a combination of the two is known as Atmospheric Refraction. 

Rayleigh scattering:

The sky appears blue to our eyes because of Rayleigh’s scattering. Rayleigh scattering is when the light comes into contact with  molecules in the atmosphere and is scattered in all direction. Rayleigh scattering is more effective for shorter wavelength. The relation between scattered light intensity and wavelength  is given as I14 . The strong wavelength dependance of Rayleigh scattering enhances the shorter wavelength, giving us the blue sky.

What is the exact sky colour?

The exact shade of blue depends on the amount of dust in the atmosphere and the time of day. The blue colour of the sky also changes with the seasons. In the summer, the sky is lighter and bluer due to more blue dust in the atmosphere. In the winter, the sky becomes darker and more navy blue due to less blue dust in the atmosphere.

The sky colour becomes red/orange:

Smog and dust in the air can also make the sky look blue. However, if you look up at the sky on a clear day, you can sometimes see white, orange or even red coloured clouds instead of blue ones. During the sunset/sunrise smaller wavelengths scatter away and only red light scatters less and reaches to our eyes so that we see a red/orange sky during this time.  

Conclusion:

This article explains the blue colour of the sky. The blue sky is one of the most commonly seen sights on Earth. It is generally defined as the sky in the daytime that appears blue because of Rayleigh scattering. The blue colour of the sky is caused by Rayleigh’s scattering, which is when light is scattered as it passes through the atmosphere. The blue colour of the sky is most visible in the late afternoons and early evenings. It is because the light from the sun is scattered more by the atmosphere during these times.