MCQ Detailed View

The sky appears blue because of a phenomenon known as Rayleigh scattering. This occurs when sunlight enters Earth’s atmosphere and interacts with molecules of gases such as nitrogen and oxygen.

Sunlight, although white in appearance, is actually made up of a spectrum of colors — red, orange, yellow, green, blue, indigo, and violet. Each color has a different wavelength. Blue light has a much shorter wavelength than red light, which makes it scatter more easily when it strikes the small particles in the atmosphere.

As sunlight passes through the atmosphere, the shorter wavelengths (blue and violet) are scattered in all directions by the gas molecules. However, our eyes are more sensitive to blue than to violet, and some of the violet light is absorbed by the upper atmosphere. As a result, we primarily see a blue sky.

Let’s examine the choices:

• 
  

  Option A (correct): The blue color of the sky is due to the scattering of blue light by the atmosphere. This scattering is more effective for shorter wavelengths.

  
  


• 
  

  Option B is incorrect because reflection is not the process responsible for the sky's color in this case.

  
  


• 
  

  Option C is incorrect; transmission refers to light passing through a medium without scattering.

  
  


• 
  

  Option D is a misconception — there is no physical blue cover over the Earth.

  
  

This principle is a key concept in Physics, specifically in the topic of light, optics, and atmospheric science. It explains not only why the sky is blue during the day but also why sunsets appear red — because longer wavelengths dominate when the sun is low on the horizon.

—