Medical applications of physics 0.0 / 5 ? PhysicsMedical PhysicsGCSEAQA Created by: Emily_OCreated on: 15-11-13 21:01 How are x-rays used in hospitals? To make images and CT scans; to destroy tumours at or near the body surface 1 of 26 What are ultrasound waves? Sound waves with a frequency above 20,000Hz 2 of 26 How are ultrasound waves used in medicine? Ultrasonic scanning and the destruction of kidney stones 3 of 26 What is refraction? The change of direction of light as it passes from one medium to another 4 of 26 How does a lens form an image? By refracting light 5 of 26 What is refractive index? A measure of how much a substance can refract a light ray 6 of 26 Refractive index = sin i (angle of incidence) divided by sin r (angle of refraction) 7 of 26 What is the the critical angle? The angle of incidence of a light ray in a transparent substance that produces refraction along the boundary 8 of 26 When does total internal reflection occur? When the angle of incidence of a light ray in a transparent substance is greater than the critical angle 9 of 26 How are endoscopes used? To see directly inside the body 10 of 26 What do converging (convex) lenses do to parallel rays? Focuses them to a point called the principal focus 11 of 26 What do diverging (concave) lenses do to parallel rays? Make them appear spread out as if they came from a point called the principal focus 12 of 26 How is a real image formed? By a converging lens if the object is further away than the principal focus 13 of 26 How is a virtual image formed? By a diverging lens and, if the object is nearer to the lens than the principal focus, a converging lens 14 of 26 Magnification = image height / object height 15 of 26 Iris Controls amount of light entering the eye 16 of 26 Eye lens Focuses light onto the retina 17 of 26 Retina Light-sensitive cells around the inside of the eye 18 of 26 Cillary muscles Attatched to the lens by suspensory ligaments and changes the thickness of the eye lens 19 of 26 Pupil Central hole formed by the iris where light enters the eye 20 of 26 Cornea Transparent layer that protects the eye and helps to focus light onto the retina 21 of 26 What causes long sightedness? The eyeball being too short or the eye lens being unable to focus 22 of 26 What causes short sightedness? The eyeball being too long or the eye lens being unable to focus 23 of 26 What type of lens is used to cure long sightedness? Converging 24 of 26 What type of lens is used to cure short sightedness? Diverging 25 of 26 Power of a lens equation P = 1 / f (P - power in dioptres, D ; f - focal length in metres, m 26 of 26
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