CBSE Class 10 Answered

Wavelengths of red and blue lights are 7000 A° and 4000 A°, respectively.
Fine dust particles in air and air molecules scatter blue light more effectively than red light. Blue light gets scattered all around the sky. Whichever direction we look some of the scattered blue light reaches us.
Since we see the blue light from every where overhead. The sky looks blue.

            As we look closer to the horizon, the sky appears much paler in colour. To reach our eye, the scattered blue light must pass longer distance through the air. Blue light gets scattered further more. Less blue light manages to reach our eyes. The colour of the sky near the horizon appears paler or white. Near the land it has been scattered to the point when the affect cannot be noticed.