When a beam of white light passes through a region having very fine dust particles, the colour of light mainly scattered in that region is :

According to the principles of scattering of light, very fine particles in the atmosphere (such as air molecules and fine dust) have sizes smaller than the wavelength of visible light. These fine particles are more effective in scattering light of shorter wavelengths (at the blue end of the spectrum) than light of longer wavelengths (at the red end). Therefore, when white light passes through a region with very fine dust particles, blue light is mainly scattered.

• Option A (Red): Incorrect. Red light has a longer wavelength and is scattered least by very fine particles.
• Option B (Orange): Incorrect. Orange has a longer wavelength than blue and is not scattered predominantly by fine particles.
• Option C (Blue): Correct. Shorter wavelengths like blue are scattered most efficiently by very fine particles.
• Option D (Yellow): Incorrect. Yellow light has a longer wavelength than blue and is scattered much less.