A60-gram sample of radioactive isotope is measured after two half-lives have passed. what pair of percentages describe the sample after two-half lives? a.) 50% unchanged and 50% stable b.) 25% unchanged and 75% stable c.) 12.5% unchanged and 87.5% stable d.) 75% unchanged and 25% stable

B.) 25% unchanged and 75% stable

Explanation:

Now, to calculate the initial amount of radioactive isotope

where,

a = amount of reactant left after n-half lives = 60 g

= Initial amount of the reactant = ?

n = number of half lives= 2

Putting values in above equation, we get:

Thus percentage of sample unchanged=

The percentage of sample decayed or has become stable=

B. 25% unchanged and 75% stable

Explanation:

Edge 2021

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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