Which of the following is NOT a property of metals? MCQ with Answer and Explanation

Explanation:
The stratospheric ozone layer absorbs the majority of the sun's harmful ultraviolet (UV-B and UV-C) radiation, preventing it from reaching Earth's surface. UV can cause skin cancer, cataracts, and damage to ecosystems. Ozone depletion is caused by CFCs (chlorofluorocarbons). Infrared is associated with heat, visible light is mostly harmless, radio waves are not absorbed by ozone.

Explanation:
Ozone (O₃) is a powerful disinfectant that decomposes to O₂, leaving no residual taste or odor. However, it must be generated on-site and provides no lasting protection. Chlorine leaves residual.

Explanation:
The half-life is the time required for half of the radioactive atoms to decay. After 10 years (1 half-life), 1/2 remains. After 20 years (2 half-lives), 1/4 remains. After 30 years (3 half-lives), the fraction remaining is (1/2)^3 = 1/8. Thus, one-eighth of the original sample will remain.