# Atoms and Nuclei-Radioactive Decay Law (KVPY (Kishore Vaigyanik Protsahan Yojana) Stream SB-SX (Class 12 & 1st Year B.Sc.) Physics): Questions 1 - 3 of 3

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## Question number: 1

» Atoms and Nuclei » Radioactive Decay Law

Appeared in Year: 2012

MCQ▾

### Question

A parent nucleus X is decaying into daughter nucleus Y which in turn decays to Z. The half-lives of X and Y are 4000 years and 20 years respectively. In a certain sample, it is found that the number of Y nuclei hardly changes with time. If the number of X nuclei in the sample is 4 × 1020, the number of Y nuclei present in it is –

### Choices

Choice (4) Response

a.

b.

c.

d.

## Question number: 2

» Atoms and Nuclei » Radioactive Decay Law

Appeared in Year: 2012

MCQ▾

### Question

A radioactive nucleus A has a single decay mode with half-life 𝜏A. Another radioactive nucleus B has two decay modes 1 and 2. If decay mode 2 were absent, the half-life of B would have been. If decay mode 1 were absent, the half – life of B would have been. If the actual half – life of B is , then the ratio is –

### Choices

Choice (4) Response

a.

b.

1

c.

d.

## Question number: 3

» Atoms and Nuclei » Radioactive Decay Law

MCQ▾

### Question

A parent nucleus X is decaying into daughter nucleus Y which in turn decays to Z. The half-lives of X and Y are 6000 years and 30 years respectively. In a certain sample, it is found that the number of Y nuclei hardly change with time. If the number of X nuclei in the sample is the number of Y nuclei present in it is –

### Choices

Choice (4) Response

a.

b.

c.

d.

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