AQA A LEVEL PHYSICS 7408/3BB PAPER 3 SECTION B MEDICAL PHYSICS VERSION 1.0 FINAL QUESTION PAPERS & MERGED MARKING SCHEME | JUNE 2023

AQA A-level PHYSICS 7408/3BB Paper 3 Section B Medical physics Version: 1.0 Final *JUN23 74083bB01* IB/M/Jun23/E 7 7408/3BB For Examiner’s Use Question Mark 1 2 3 4 5 TOTAL Thursday 15 June 2023 Morning Materials For this paper you must have: • a pencil and a ruler • a scientific calculator • a Data and Formulae Booklet • a protractor. Instructions • Use black ink or black ball -point pen. • Fill in the boxes at the top of this page. • Answer all questions. • You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s). • Do all rough work in this book. Cross through any work you do not want to be marked. • Show all your working. Information • The marks for questions are shown in brackets . • The maximum mark for thi s paper is 35. • You are expected to use a scientific calculator where appropriate. • A Data and Formulae Booklet is provided as a loose insert. Please write clearly in block capitals. Centre number Candidate number Surname Forename(s) Candidate signature I declare this is my own work. A-level PHYSICS Paper 3 Section B Medical physics Time allowed: The total time for both sections of this paper is 2 hours. You are advised to spend approximately 50 minutes on this section. 2 *02* IB/M/Jun23/ 7408/3BB Do not write outside the box Section B Answer all questions in this section . 0 1 Brachytherapy is used to treat small tumours. In this technique a sealed radioactive source is placed inside a patient’s body next to the tumour. Explain one advantage of using beta radiation rather than gamma radiation in brachytherapy. [2 marks] 2 3 *03* Turn over ► IB/M/Jun23/ 7408/3BB Do not write outside the box 0 2 Electrophoretic screens are used in handheld electronic devices. The screen contains individual squares known as pixels. Pixels can be changed independently from light to dark to create the shapes of letters and numbers. An external light source is needed in order to read the screen. Figure 1 shows a letter formed by three electrophoretic screens that have different pixel line densities. Pixel line density is the number of pixels along a 1.0 cm length of the screen. Figure 1 0 2 . 1 A particular screen is designed so that two dark pixels separated by one light pixel cannot be resolved as separate image s by the eye when viewed from a distance of 0.50 m . Determine , in pixels per cm, the minimum pixel line density required for this screen. typical diameter of cones in a human eye at the fovea = 1.5 μm typical length of the human eye = 21 mm [3 marks] pixels per cm = Question 2 continues on the next page