P3.1 Medical applications of physics
Can you…?
P3.1.1 X-rays
Compare the wavelength of X-rays to the diameter of an atom
Describe how X-rays affect photographic film, and how they interact with bone and tissue
Outline some uses of X-rays for diagnosis and treatment of some medical conditions
(including charge-coupled devices, or CCDs)
Outline the precautions that needed when using X-ray machines and CT scanners
P3.1.2 Ultrasound
Define ‘ultrasound’ in relation to the range of human hearing
Describe how ultrasound waves can be partially reflected when they meet a boundary
between one medium and another, and how the time taken for reflections to reach a
detector can be used
Calculate the distance between interfaces in various media using:
s=v x t
Use data from oscilloscope traces in the above equation
Give examples of how ultrasound waves can be used in medicine
Compare the medical use of ultrasound and X-rays
Evaluate advantages and disadvantages of using ultrasound, X-rays and CT scans
P3.1.3 Lenses
Define the term ‘refraction’ and state that a lens forms an image by refracting light
Describe the effect of a convex or converging lens on parallel rays of light
Define the term ‘focal length’
Calculate the refractive index using angles of incidence (i) and refraction (r)
Describe how the nature of an image is defined by its size relative to the object, whether
it is upright or inverted and whether it is real or virtual
Describe the nature of images produced by a converging lens for an object placed at
different distances to the lens
Outline the use of converging lenses as magnifying glasses
Describe the nature of an image produced by a concave or diverging lens
Construct ray diagrams to show the formation of images by converging and diverging
lenses, and complete such diagrams drawn on graph paper
Draw and interpret ray diagrams in order to determine the nature of the image
P3.1.4 The eye
Describe the structure of the eye, including the functions of the retina, lens, cornea,
pupil/iris, ciliary muscle and suspensory ligaments
Explain how long sight and short sight are causes, and how convex and concave lenses
can be used to correct such vision to produce an image on the retina
Evaluate the use of different lenses for the correction of defects of vision
Describe the range of vision in terms of near point and far point, including distances
Compare the structure of the eye with a camera
Calculate the power (P, expressed in dioptres, D) of a lens using the equation:
P=1/f
Explain how the focal length of a lens is determined using the refractive index of the
material and the curvature of the two surfaces of the lens
(HT) Relate the flatness of a lens to its refractive index, allowing for thinner lenses
P3.1.5 Other applications using light
Describe total internal reflection and explain what is meant by ‘critical angle’ (c)
(HT) Calculate refractive index as 1 / sin c
Give examples of how visible light can be sent along optical fibres
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