What is a heterogeneous mixture

A heterogeneous mixture is simply any mixture that is not uniform in composition - it's a non-uniform mixture of smaller constituent parts.

when all components are visible in the mixture

Explanation:

Basically you are able to see everything that is in there separately

- Water and Oil

- Cold Water and Salt

- Water and Sand

the ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (uvr) from the sun, protecting life on earth from its potentially harmful effects. when the sky is clear, there is an inverse relationship between stratospheric ozone and solar uvr measured at the earth's surface.