Sun blocks are either chemical or physical. Oils, lotions, and creams all contain chemical blocks. On the other hand, zinc oxide, the white or colored clay-looking material you see on some people, is a physical sun block. This illustrates the use of:

filtering agent

Explanation:

The sun's ultra violet rays are harmful to skin of the people. The skin gets harmed and tanned when exposed to the sunlight for a longer period of time. People use different methods and ways to get rid of these and avoid exposing themselves to the sun.

People use different lotions, SPF creams, sun creams so as to protect their skin form the harmful ultra violet rays. Some of these are chemical barriers while some are physical barriers to the rays.

The chemical blockers work in such a way that they absorb the harmful rays and prevent the harmful rays from penetrating the skin.

Whereas a physical blocker such as the zinc oxide or titanium dioxide, they sit on the top surface of the skin and protect the skin by scattering the light away from the skin. Zinc oxide is much better than titanium dioxide as the zinc oxide blocks both deep penetrating ultra violate A rays as well as short wave B rays. They have large size particle that have an opaque white look.

so is this a rhetorical question?