Numerical Problem No. 1 (Unit-18 Radioactivity) Physics SSC - II (Class 10) - National Book Foundation

A radioactive substance has a half-life of eight months. In how much time, three-fourths of the substance will decay? Ans. (16 months)

Data Given:

Half-life of radioactive substance= T₁/₂ = 8 months 

Decay substance = 3/4

To Find:

Time taken during which three-fourths of the substance will decay = t = ?

Solution:

During 1st Half-life the substance will decay = 1/2 

During 2nd Half-life the substance will decay = 3/4

Thus, the number of half-life is = 2

Hence by using the formula

Time = Number of Half-lives ｘ half-life ( T₁/₂ )

by putting values

Time = 2 ｘ 8 months

Time = 16 months   -----Ans

Similar Questions (SLO Based)

The half-life of a radioactive element is 10 minutes. If the initial count rate is 368 counts per minute, find the time by which, the count rate would reach 23 counts per minute. Ans. (40 minutes)

Carbon-14 has a half-life of 5730 years. How long will it take for the quantity of carbon-14 in a sample to drop to one-eighth of the initial quantity? Ans. (1.72 ｘ 10⁴ years).

In 420 days, the activity of a sample of polonium (Po) to one-eighth of its initial value. What is the half-life of polonium? Ans. (140 days).

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