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Medical Physics 2024 | 204 Questions and Answers with Complete Solutions 100% Correct
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Medical Physics 2024 | 204 Questions and Answers with Complete Solutions 100% Correct
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Medical physics certification Medical Physics 2024 | 204 Questions and Answers with Complete Solutions 100% Correct The diagram represents a simplified version of a normal eye, with no sight defects, looking at a distant point object. Complete the paths of the two rays. - Answer rays refracted inwards at cornea % rays refracted inwards at lens % rays focused at optic axis on retina % (b) Describe the distribution of receptors over the retina. - Answer only cones at fovea %moving away from fovea, more rods, less cones % State the purpose of the iris. - Answer (c)(i) to control the intensity of light reaching retina % (ii) Describe how this purpose is achieved when the eye is exposed to bright light. - Answer (c)(ii) forms a small pupil % (2) State what is meant by accommodation. - Answer (d)(i) accommodation: ability of the eye/lens to (change and) focus on different object distances [adjustment of the eye/lens to form a clearly focused image on the retina] (ii) Describe how accommodation is achieved. - Answer (d)(ii) changing the shape of the lens or using the ciliary muscles State two ways of ensuring good electrical contact between the electrodes and the person. - Answer Sketch, on the axes below, the waveform that you would expect to obtain. Label the axes with appropriate scales. Mark on the waveform where the following occur: (i) atrial depolarisation (ii) ventricular depolarisation (iii) ventricularrepolarisation - Answer Medical physics certification State the frequency of sound at which the normal ear is most sensitive. - Answer (b) State the main features of hearing loss in terms of frequency response for (i) age related hearing loss, (ii) noise related hearing loss. - Answer (c) At the site of a machine in a factory, a sound meter was used to measure the sound level. The relative intensity level with the machine operating was 86 dB. The sound intensity reaching the meter when the machine was not operating was 7.0 × 10^ -5 Wm-2 (i) Show that with the machine operating, the sound intensity reaching the meter was about4×10^ -4 Wm . (ii) Calculate the relative intensity level due to the machine alone. - Answer The diagram shows a rotating -anode X -ray tube. Complete the labelling of the three numbered arrows in the diagram. - Answer (b) Explain why the anode (i) is rotated, (ii) has a bevelled edge. - Answer (c) Define for a material, (i) the linear attenuation coefficient, μ, (ii) the half thickness. - Answer (d) A monochromatic X -ray beam of intensity 6.0 Wm -2 is incident on an aluminium sheet of thickness 2.0 mm. For these X -rays, the half -value thickness of aluminium is 3.2 mm. Calculate the intensity of the transmitted beam - Answer Describe how the rods and cones are distributed over the surface of the retina. - Answer On the axes below sketch three curves to show how the response of each of the three types of cone found in the retina varies with the wavelength of light. 1 (b) Medical physics certification Label each of the three curves with the cone colour to which it refers. - Answer 1 (c) State the condition that must be satisfied for two objects to be resolved as individual images on the retina. - Answer Explain how the resolution of the image of an object seen in very dim white light compares to that of the image of the same object seen in bright white light. - Answer Colours seen in bright light, but black and white in very dim light Good detail in bright light, but much less detail in very dim light Sound waves are incident on the ear canal of a normal human ear. Describe the physical processes involved in the transmission of the energy from the air through to the inner ear. Include an outline of how the variations in air pressure in the ear canal are amplified to produce greater pressure variations in the inner ear. - Answer Define intensity of sound. - Answer A human ear has a threshold of hearing of 54 dB at a given frequency. Calculate the intensity of sound incident on the ear at this frequency. Give your answer to an appropriate number of significant figures. - Answer Figure 1 shows an ultrasound transducer used in an A -scan. Outline, with reference to the diagram, the process by which the transducer produces a short pulse of ultrasound. - Answer Calculate the percentage of the incident ultrasound which would be transmitted into the skin when incident on an air -skin boundary. acoustic impedance of air = 4.29 × 102 kg m -2 s-1 acoustic impedance of skin = 1.65 × 106 kg m -2 s-1 - Answer When obtaining the ultrasound image of an unborn foetus, a coupling gel is used. Explain why a coupling gel is needed and state the property of the gel that ensures a good quality image. - Answer Medical physics certification State the value of the resting potential. - Answer Name the process involved between points A and B on the curve and describe the ion movement which produces this change. - Answer Name the process involved between points C and D on the curve and describe the ion movement which produces this change. - Answer State the changes which occur in a normal eye when the eye changes from focussing on a distant object to focussing on a near object, both objects being viewed in bright light the eye changes from viewing an object in very dim light to viewing the same object in bright light. - Answer State two differences in the perceived image of a coloured object viewed in bright white light compared to the perceived image of the same object viewed in very dim white light. - Answer A patient's eye is astigmatic. State the effect of astigmatism on the image produced by the defective eye. - Answer State the usual cause of astigmatism - Answer State the shape of lens used to correct astigmatism. - Answer A sound source of constant output power is used to generate a sound which is measured using a sound meter. When set to the dB scale, the sound meter displayed 60 dB as the reading when the frequency of the sound was 1 kHz. State and explain what the reading would be for a sound of frequency 1 kHz if the meter was changed to the dBA scale. - Answer State and explain what would happen to the reading on each scale if the frequency of the sound was changed to 500 Hz. - AnswerThe benefits of buying summaries with Stuvia:
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