Physics Crash Course NEET>Chapter 20 - Atoms and Nuclei>Level 1>Q 22

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IMPORTANT

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The half life period of a radioactive element $x$ is same as the mean life time of another radioactive element $y .$ Initially they have the same number of atoms. Then:

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Important Questions on Atoms and Nuclei

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IMPORTANT

Physics Crash Course NEET>Chapter 20 - Atoms and Nuclei>Level 1>Q 23

The ratio of amounts of radioactive substance

X

and

Y

at any instant is

1 : 4

. The half-life of substance

X

is

18

hours and of

Y

is

12

hours. After three days, the ratio of the amounts of the two substances will be

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Physics Crash Course NEET>Chapter 20 - Atoms and Nuclei>Level 1>Q 24

The half life of Thorium

({Th}^{232})

is

1.4 \times 10^{10} years

. Then, the fraction of Thorium atoms decaying per year is very nearly,

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Physics Crash Course NEET>Chapter 20 - Atoms and Nuclei>Level 1>Q 25

Half-lives of two radioactive substances

A

and

B

are, respectively,

20 minutes

and

40 minutes

. Initially, the samples of

A

and

B

have the equal number of nuclei. After

80 minutes

, the ratio of remaining number of

A

and

B

nuclei are

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Physics Crash Course NEET>Chapter 20 - Atoms and Nuclei>Level 1>Q 26

A nucleus

X^{m}

emits one

α

and two

β^{-}

-particles. The resulting nucleus is

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Physics Crash Course NEET>Chapter 20 - Atoms and Nuclei>Level 1>Q 27

Half life of radioactive element is

12.5

Hour and its quantity is

256 g

. After how much time its quantity will remain

1 g

:-

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Physics Crash Course NEET>Chapter 20 - Atoms and Nuclei>Level 1>Q 28

If the half-life of a substance is

38 days

and its quantity is

10.38 g

. Then the quantity remaining left after

19 days

will be:

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Physics Crash Course NEET>Chapter 20 - Atoms and Nuclei>Level 1>Q 29

A sample of the radioactive elements containing

4 \times 10^{16}

active nuclei. The half-life of an element is

10 days

, then the number or decayed nuclei after

30 days

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Physics Crash Course NEET>Chapter 20 - Atoms and Nuclei>Level 1>Q 30

X

-rays are incident on a target metal atom having

30

neutrons. The ratio of the atomic radius of the target atom and

{}_{2}^{4}{He}

is

14^{(\frac{1}{3})}

. The atomic number of the target atom is