1. P4 Radiation for Life 6 mark questions (and mark schemes)

6. Ultrasound can be used in foetal scanning. A three-dimensional (3-D) scan uses computer technology and gives a more detailed image than a conventional two- dimensional (2-D) scan. Explain how ultrasound is used in foetal scanning and why a pregnant woman is scanned with ultrasound but is never X-rayed.

7. Level 3 Detailed explanation of how ultrasound is used in foetal scanning with reference to the densities and speed of sound in adjoining tissues and mention of why X-rays would not be used. All information in answer is relevant, clear, organised and presented in a structured and coherent format. Specialist terms are used appropriately. Few, if any, errors in grammar, punctuation and spelling. (5 – 6 marks) Relevant points include: Pulse of ultrasound sent into patients body At each boundary some of the ultrasound is reflected (the rest is transmitted) Return echoes are recorded and used to build up an image of the internal structure. A gel is placed on the body to prevent reflection of the ultrasound from the surface of the skin. Gel is needed to ensure a good image is obtained Reflections from different layers return at different times from different depths. The depth of each layer is calculated using the speed equation Distance = speed x time the distance calculated is there and back so needs to be halved The proportion of ultrasound reflected depends on the densities of adjoining tissues The proportion of ultrasound reflected depends on the speed of sound in adjoining tissues If tissues are very different then most of the ultrasound is reflected A doppler ultrasound is used to detect movement and can be used to measure the foetal heart rate ADVANTAGES OF ULTRASOUND ultrasound differentiates between soft tissues better than X-rays. ultrasound does not damage living cells. X-rays can kill cells or bring about changes in them that can lead to the development of cancers. Level 2 Limited explanation of how ultrasound is used in foetal scanning. An appreciation of the advantages of ultrasound over X-rays. No mention of X-rays scores the lower mark. For the most part the information is relevant and presented in a structured and coherent format. Specialist terms are used for the most part appropriately. There are occasional errors in grammar, punctuation and spelling. (3 – 4 marks) Level 1 An incomplete answer explaining few aspects of the process. Answer may be simplistic. There may be limited use of specialist terms. Errors of grammar, punctuation and spelling prevent communication of the science. (1 – 2 marks) Level 0 Insufficient or irrelevant science. Answer not worthy of credit. (0 marks)

8. 6 Mark Question on THE PLUG Explain the functions of the different wires in the plug AND how a fuse protects the appliance if it develops a fault.

9. 6 Mark Question on THE PLUG Live wire carries current to the appliance (1 mark) Neutral wire completes the circuit and is kept at 0V (1 mark) Earth wire is a safety feature that ‘earths’ appliances with metal cases (1 mark) Wire in fuse melts if current gets too large, stopping current (1 mark) This prevents overheating which may cause fire (1 mark) Prevents further damage to the appliance(1 mark)