What part of the microscope is used to adjust the amount of light that shines through the slide

You are to give ampicillin with a recommended dose of 25mg/kg to a child with a mass of 29kg. if stock on hand is 250mg/capsule how many capsules should be given?

Tin has ten stable isotopes. the heaviest, 124sn, makes up 5.80% of naturally occuring tin atoms. how many atoms of 124sn are present in 82.0 g of naturally occurring tin? what is the total mass of the 124sn atoms in this sample?

What happens to isotopes that are unstable?