IGCSE Physics (0625) -Unit 5. Atomic physics-5.2.1 Detection of radioactivity-Paper 2

Question

When measuring the emissions from a radioactive rock brought into the laboratory, a teacher

 mentions that background radiation must be taken into account. 5.2.1

What is this background radiation?

A infra-red radiation from warm objects in the laboratory

B infra-red radiation from the Sun

C ionising radiation from the radioactive rock brought into the laboratory

D ionising radiation in the laboratory when the radioactive rock is not present

Answer/Explanation

Ans: D

Question

A student measures the level of radiation emitted from a radioactive substance. He places a

detector very close to the substance. He puts different absorbers between the radioactive

substance and the detector.

                 

The student’s results are shown. These results are corrected for background radiation.

absorber

counter reading counts per minute

none

95

thin paper

52

few mm of aluminium

52

several cm of lead

12

Which types of radiation are being emitted by the substance?

  1. α-particles and β-particles only

  2. α-particles and γ-rays only

  3. β-particles and γ-rays only

  4. α-particles, β-particles and γ-rays

Answer/Explanation

Ans: B

Question

The diagram shows the paths of three different types of radiation, X, Y and Z.

       

Which row in the table correctly identifies X, Y and Z? 

 

X

Y

Z

A

α-particles

β-particles

γ-rays

B

β-particles

α-particles

γ-rays

C

β-particles

γ-rays

α-particles

D

γ-rays

α-particles

β-particles

Answer/Explanation

Ans: B

Question

In a laboratory, a detector of ionising radiation records an average background count rate of

8 counts per second.

               

A radioactive source is now placed close to the detector. The count rate on the detector rises to

200 counts per second.

What is the count rate due to radiation from the radioactive source?

A 25 counts / s

B 192 counts / s

C 200 counts / s

D 208 counts / s

Answer/Explanation

Ans: B

Question

The arrangement shown is used to check whether the flour inside a cardboard packet is above a

certain level. If it is above this level, the flour absorbs the radiation from the source so that it

doesn’t reach the detector.

                   

Which type of radiation is suitable to use?

A. α-particles only

B.β-particles only

C. either α-particles or β-particles

D. γ-rays only

Answer/Explanation

Ans: B

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