Question

Half life of a radioactive sample is 10 days. If originally 100mg of thee substance was present what will be the activity after 5 days

Answer 1

Given, T = 10 days

t = ?

where, t is the time period in which the atom fully disintegrates.

No. of atoms disintegrated = N0

No. of atoms left after time t,

N = N0 - N0 = 0

No. of half lives in time t days,

n = t/T = t/10

No. of nuclei left after n half lives is given by :

N = N0 (12)n

0 = N0 (12)t/10

0 = (1/2)t/10

or 2 t/10 = ∞

On solving we get :

t = ∞ days

Hence, the atom will fully disintegrate in infinite days.

Answer 2

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$\it\huge\mathfrak\red{Answer}$]

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For 10 Days

2 - 2/2 = 1

For 20 Days

1 - 1/2 = 1/2

For 30 Days

1/2 - (1/2)/2 = 1/2 - 1/4 = 1/4

For 40 Days

1/4 - 1/4/2 = 1/4 - 1/8 = 1/8

After 40 Days 1/8 gm will remain

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$\it\huge\mathfrak\red{Thanks}$]

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