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Question 19N.3.HL.TZ0.14a(ii)

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Date November 2019 Marks available [Maximum mark: 4] Reference code 19N.3.HL.TZ0.14a(ii)
Level HL Paper 3 Time zone TZ0
Command term Explain, State Question number a(ii) Adapted from N/A
a(ii).
[Maximum mark: 4]
19N.3.HL.TZ0.14a(ii)

An X-ray beam, of intensity I0, 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 It and the intensity emerging from the blood is Ib.

The following data are available.

Mass absorption coefficient of tissue    = 0.379 cm2 g–1
Mass absorption coefficient of blood     = 0.385 cm2 g–1
Density of tissue                                    = 1.10 × 103 kg m–3
Density of blood                                     = 1.06 × 103 kg m–3

(a(ii))

State and explain, with reference to you answer in (a)(i), what needs to be done to produce a clear image of the leg artery using X-rays.

[4]

Markscheme

the difference between intensities is negligible so no contrast ✔

modifying the blood is easier than modifying the soft tissue ✔

increase absorption of X-rays in the blood ✔

by injecting/introducing a liquid/chemical/contrast medium ✔

with large mass absorption coefficient/nontoxic/higher density ✔

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