Red light being of longest wavelength scatters least and reaches our eye while blue colour scatters most.

When pesticides and other non-biodegradable chemicals enter the food chain, these get accumulated progressively at each trophic level and this is known as biological magnification.

The sky appears blue due to excessive scattering of blue light by the air molecules.

When a beam of light passes from a denser medium to a rarer medium, its velocity increases and wavelength decreases, per frequency remains constant.

The white solid, lead carbonate is heated and decomposes into yellow coloured lead oxide and carbon dioxide. So, “X” is lead oxide.