Answer: spectroscopy
Spectroscopy is the separation of the light in the different wavelengths and spectrophotometry measures the intensities of the different components of the light to get the composition of substances.
Answer:
Let No be initial no of atoms
N = N0 / 2 after 1 half-life
N = N0 / 4 after 2 half-lives
So after 2 half-lives 20 of the 80 atoms remain
the polluted urban environment affects the health and quality of life