Figure 1 shows apparatus used to investigate the inverse-square law for gamma radiation. A sealed source that emits gamma radiation is held in a socket attached to clamp B. The vertical distance between the open end of the source and the bench is 138 mm. A radiation detector, positioned vertically above the source, is attached to clamp T. A student is told not to move the stands closer together. Describe a procedure for the student to find the value of d, the vertical distance between the open end of the source and the bench. In your answer, annotate Figure 1 to show how a set-square can be used in this procedure.

A-Level AQA Physics Limitation of Physical Measurements: Figure 1 shows apparatus used to

Figure 1 shows apparatus used to investigate the inverse-square law for gamma radiation - AQA - A-Level Physics - Question 1 - 2021 - Paper 3

Question 1

Figure 1 shows apparatus used to investigate the inverse-square law for gamma radiation. A sealed source that emits gamma radiation is held in a socket attached to ... show full transcript

Worked Solution & Example Answer:Figure 1 shows apparatus used to investigate the inverse-square law for gamma radiation - AQA - A-Level Physics - Question 1 - 2021 - Paper 3

Step 1

Describe a procedure for the student to find the value of d

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Answer

Set Up the Apparatus: Ensure the setup in Figure 1 is correctly positioned with the radiation detector attached to clamp T and the sealed source held in clamp B.
Use of Set-Square: Place a recognizable set-square against the detector to ensure it is perpendicular to the bench.
Measure the Height: Using a ruler, measure the height from the bottom edge of the set-square (where it meets the bench) to the bottom edge of the source.
Calculate the Distance: Subtract 138 mm (the distance from the bench to the source) from the measured height to find the value of d.
Annotation of Figure 1: Annotate Figure 1 to show the set-square's position ensuring its right angle is clearly indicated at the detector's base.

Step 2

Before the source was brought into the room, a background count C1 was recorded.

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Answer

C1 = 630 counts in 15 minutes.

Step 3

With the source and detector in the positions shown in Figure 1, d = 530 mm.

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Answer

Separate counts C2, C3 and C4 are recorded such that C2 = 90 counts in 100 s, C3 = 117 counts in 100 s, and C4 = 102 counts in 100 s.

Figure 1 shows apparatus used to investigate the inverse-square law for gamma radiation - AQA - A-Level Physics - Question 1 - 2021 - Paper 3

Worked Solution & Example Answer:Figure 1 shows apparatus used to investigate the inverse-square law for gamma radiation - AQA - A-Level Physics - Question 1 - 2021 - Paper 3

Describe a procedure for the student to find the value of d

Before the source was brought into the room, a background count C1 was recorded.

With the source and detector in the positions shown in Figure 1, d = 530 mm.

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