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**Q.1. For a radioactive material, half-life is 10 minutes. If initially there are 600 number of nuclei, the time taken (in minutes) for the disintegration of 450 nuclei is: (2018)A: 20B: 10C: 30D: 15Ans: **A

Solution:

A: 1/7Î»

B: 1/8Î»

C: 1/9Î»

D: 1/10Î»

Ans: A

Solution:

A: 8.4 MeV

B: 17.3 MeV

C: 19.6 MeV

D: âˆ’2.4 MeV

Ans: B

Solution:

A: 4.20 Ã— 10

B: 8.40 Ã— 10

C: 1.96 Ã— 10

D: 3.92 Ã— 10

Ans: A

Solution:

Ratio of X:Y is given = 1:7

That is,

â‡’ 7m

Let, the initial total mass is m.

Therefore, time taken to become 1/8 unstable part

= 3 x T

= 3 x 1.4 x 10

= 4.2 x 10

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