Gamma Question Bank for Engineering Physics>Chapter 29 - Nuclei>EXERCISE 13.2>Q 8

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Half life of a radioactive element is $40$ minute. What amount will remain undecayed after $4$ hour?

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Important Questions on Nuclei

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Gamma Question Bank for Engineering Physics>Chapter 29 - Nuclei>EXERCISE 13.2>Q 9

A radioactive substance decays by two different processes having half lives

t_{1}

and

t_{2}

respectively. When both decays take place simultaneously, the effective half life of substance is

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Gamma Question Bank for Engineering Physics>Chapter 29 - Nuclei>EXERCISE 13.2>Q 10

A freshly prepared radioactive source (half life

= 4

hrs) emits radiations of intensity which is

32

times the permissible level. The minimum time (in hr) after which it would be safe to work with this source is

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Gamma Question Bank for Engineering Physics>Chapter 29 - Nuclei>EXERCISE 13.2>Q 11

Consider the following decay :

{}^{220}X \to {}^{216}Y + α + 5.5 MeV

Kinetic energy of

α

particle is

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Gamma Question Bank for Engineering Physics>Chapter 29 - Nuclei>EXERCISE 13.2>Q 12

A radioactive substance decays to

1 / 16^{th}

of its initial activity in

40

days. The half-life of the radioactive substance expressed in days is :-

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Gamma Question Bank for Engineering Physics>Chapter 29 - Nuclei>EXERCISE 13.2>Q 13

When an $U^{238}$ nucleus originally at rest, decays by emitting an alpha particle having speed $u$ , the recoil speed of the residual nucleus is

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Gamma Question Bank for Engineering Physics>Chapter 29 - Nuclei>EXERCISE 13.2>Q 14

A radioactive sample, at any instant, has its disintegration rate $5000 disintegration per minute$ . After

5 \min

, the rate is $1250 disintegration per minute$ . Then, the decay constant (per

\min

) is

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Gamma Question Bank for Engineering Physics>Chapter 29 - Nuclei>EXERCISE 13.2>Q 15

In the nuclear fusion reaction

{}_{1}^{2}H + {}_{1}^{3}H \overset{}{\to} {}_{2}^{4}{He} + n

. It is given that the repulsive potential energy between the two nuclei is

~ 7.7 \times 10^{- 14} J

, the temperature at which the gases must be heated to initiate the reaction is nearly

[

Boltzmann's constant

k = 1.38 \times 10^{- 23} J K^{- 1}]

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Gamma Question Bank for Engineering Physics>Chapter 29 - Nuclei>EXERCISE 13.2>Q 16

The activity of a radioactive sample is

1.6 curie

and its half-life is

2.5

days. Its activity after

10

days will be,