Answer:
Magnitude
Explanation:
Astronomers define star brightness in terms of magnitude (how bright the star appears from Earth)
Half-life is basically how long it takes for a radioactive molecule to get to 1/2 of its original mass.
so if sodium 24 mass was 5g and it's half life was 24years then:
after every 24years 1/2 of 5g would have decayed. so in 48years there will only be 2.5g left.
