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Question:

Using a nuclear counter, the count rate of emitted particles from a radioactive source is measured. At t=0 it was 1600 counts per second and at t=8 seconds it was 100 counts per second. The count rate observed, as counts per second, at t=6 seconds is close to 150, 200, 400, 360

360

400

200

150

Solution:

The correct option is C 200
At t=0, A₀=dN/dt=1600 C/s
At t=8s, A=100 C/s
A/A₀=1/16 in 8 sec
Therefore half life is t₁/₂=2 sec
∴Activity at t=6 will be 1600(1/2)³=200 C/s
∴correct answer is (3).