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CAIE A-Level Physics A2 24.2 Production and Use of X Rays Questions

Practise analysing X-ray production, minimum wavelength, attenuation, image contrast and CT reconstruction, including radiation exposure comparisons.

Syllabus
2028–2030
Course
Physics 9702
Level
A2

Exam points

  • explain X-ray production and calculate minimum wavelength from accelerating p.d.
  • interpret X-ray image contrast from material attenuation and transmitted intensity
  • calculate X-ray transmission or absorption using I = I?e??x
  • explain CT reconstruction from multiple angled images and sections
  • evaluate CT against single X-ray imaging, including 3D information and radiation exposure

Covered syllabus points

24.2.1—That X-rays are produced by electron bombardment of a metal target and24.2.2—The use of X-rays in imaging internal body structures24.2.3—I = I0e–µx for the attenuation of X-rays in matter24.2.4—Computed tomography (CT) scanning produces a 3D image of an internal

Question 1

[Maximum number: 7]

Question (a)

(a)

In computed tomography (CT scanning), it is necessary to take a series of many X-ray images. Outline briefly the principles of CT scanning.

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Question (b)

(b)

A student creates a model for CT scanning.

A section is divided into four voxels, with pixel numbers A, B, C and D , as shown in Fig. 9.1.

Fig. 9.1

Fig. 9.1

The section is viewed from four different directions V1, V2, V3\mathrm{V}_{1}, \mathrm{~V}_{2}, \mathrm{~V}_{3} and V4\mathrm{V}_{4}, as shown in Fig. 9.1.
The detector readings for each direction are noted and then summed. The result is shown in Fig. 9.2.

Fig. 9.2

Fig. 9.2

The background count is 26 .
Determine the pixel numbers A, B, C and D as shown in Fig. 9.1.
A B
D
C

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