Melanin is a natural pigment that gives color to human skin, hair, and the iris. It acts as a protective shield against certain types of radiation. Option 1, ultraviolet (UV) radiation, is the correct answer. UV radiation is a type of electromagnetic radiation that comes from the sun and artificial sources like tanning beds. It is known to cause harmful effects on the skin, such as sunburn, premature aging, and an increased risk of skin cancer.

Melanin plays a crucial role in protecting the skin from these harmful effects by absorbing and scattering UV radiation. It acts as a natural sunscreen, preventing excessive penetration of UV rays into the underlying layers of the skin. Melanin absorbs UV radiation and dissipates the energy as heat, reducing the damage caused by the radiation. This protective mechanism helps to prevent DNA damage, mutations, and potential skin cancer development.

Options 2, 3, and 4 (infrared radiation, X-ray radiation, and shortwave radio radiation) are incorrect because melanin does not provide protection against these types of radiation. Infrared radiation is felt as heat but does not have the same damaging effects as UV radiation. X-ray radiation and shortwave radio radiation have completely different properties and effects on the human body