What is the half-life of isotope X? How many radioactive atoms of isotope X are left after
3 half-lives?
How many half-lives must have occurred if only 7
atoms of isotope X are left?

Critical mass is the of material required to produce a chain reaction. a.) minimum amount b.) atomic mass c.) precise amount d.) maximum amount

Light traveling in water, nwater = 1.33, strikes a plastic block at an angle of incidence of 51.4°; part of the beam is reflected and part is refracted. if the index of refraction of the plastic is 2.0, what is the angle made by the reflected and refracted beams?

In a series circuit the __ is the same at every point