DP Physics (last assessment 2024)

Question 19N.3.HL.TZ0.a(i)

Date	November 2019	Marks available	[Maximum mark: 3]	Reference code	19N.3.HL.TZ0.a(i)
Level	HL	Paper	3	Time zone	TZ0
Command term	Show that	Question number	a(i)	Adapted from	N/A

a(i).

[Maximum mark: 3]

19N.3.HL.TZ0.a(i)

An X-ray beam, of intensity $I_{0}$ , is used to examine the flow of blood through an artery in the leg of a patient. The beam passes through an equal thickness of blood and soft tissue.

The thickness of blood and tissue is 5.00 mm. The intensity of the X-rays emerging from the tissue is $I_{t}$ and the intensity emerging from the blood is $I_{b}$ .

The following data are available.

Mass absorption coefficient of tissue = 0.379 cm²g^–1
Mass absorption coefficient of blood = 0.385 cm²g^–1
Density of tissue = 1.10 × 10³kg m^–3
Density of blood = 1.06 × 10³kg m^–3

Show that the ratio $\frac{I_{b}}{I_{t}}$ is close to 1.

[3]

Markscheme

$μ_{t} = 0.379 \times 1.1 \times 10^{3} \times \frac{10^{3}}{10^{6}} = 0.417 « {cm}^{- 1} »$ AND $μ_{b} = 0.408 « {cm}^{- 1} »$ ✔

$\frac{I_{b}}{I_{t}} = \frac{I_{0} e^{- μ_{b} x}}{I_{0} e^{- μ_{t} x}} = e^{- (0.408 - 0.417) \times 0.5}$ ✔

$\frac{I_{b}}{I_{t}} = 1.004$ ✔

Syllabus sections

Option C: Imaging

Option C: Imaging » Option C: Imaging (Additional higher level option topics) » C.4 – Medical imaging (HL only)

Option C: Imaging » Option C: Imaging (Additional higher level option topics)

Question 19N.3.HL.TZ0.a(i)

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