First slide

Radio activity

Question

The half-life period of a radioactive substance is 5 min. The amount of substance decayed in 20 min will be

Moderate

A

93.75%
B

75%
C

25%
D

6.25%

Solution

Number half-lives in 20 min $= n = \frac{20}{5} = 4$
Fraction of material remains after four half lives $= \frac{1}{16}$
Hence fraction that decays $= 1 - \frac{1}{16} = \frac{15}{16} = 93.75 %$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App