AQA Triple Physics | Medical Applications of Physics

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  • Created by: Sam Nunn
  • Created on: 04-03-13 18:15


-X-rays are also known as radiographs.

-X-rays are used in hopsitals to make images and CT scans and to destroy tumours at or near the surface of the body.

-A flat -panle detector contains a CCD. The sensors in the CCD are covered in a layer of substances which convert x-rays to light and the light then sends electronic signals to the computor which displays the digital x-ray image.

-X-rays will pass through soft tissues but be absorbed by bones, teeth and metal objects that are not too thin.

-A radiograph shows a negative image of the bones.

-X-radiation is dangerous because it ionises substances it passes through and high doses can even kill living cells and low doses can mutate them.

-X-rays can be used to destory tumours in the human body and these have shorter wavelengths than the imaging x-rays.

-A CT scanner can produce 3D images of any internal organs.

-Ordinary x-ray machine:

. Distinguishes between bone and soft tissue

.Has a lower radiation dose

.Cheaper than CT scanner

-CT scanner:

.Distinguishes between bone and soft tissue

.Distinguishes between different type of soft tissue

.Three dimensional image

.High radiation levels

.High costs


-Sound waves above the highest frequency that humans can hear (20 000 Hz) are known as ultrasound waves.

-A transducer will detect and create pulses of ultrasound waves which will be displayed on a screen. Each of these pulses are partially reflected from the different tissue boundaries in its path and returns to the transducer, arriving at different times.

-Ultrasound is non-ionising and therefore harmless when used for scanning and reflected at different boundaries between different types of tissue so they can be used to scan organs and other types of soft tissue in the body.

-Ultrasound can be used to measure the distance between small objects using an oscilliscope. The time taken for each pulse to appear can be converted into how far away it is using a formula.

-Powerfull ultrasound waves can be used to break kidneys stones into tiny pieces which are now small enough to leave the kidney naturally.

Refractive Index

-Refractive index is a measure of how much a substance can refract a light ray.

-When a light ray travels form a transparent substance into air a a non- zero angle of incedence the light ray is always refracted away from the normal and the larger the angle of incedence is, the larger the angle of refraction.

The Endoscope

-If the angle of incedence in the glass is gradually increased, the angle of refraction increases until the refracted ray emerges along the boundary. The angle of incedence is referred to as the critical angle.

-If the angle or incidence is increased beyond the critical angle, the light ray is totally internally reflected. When total internal reflection occours, the angles of reflection at P is equal to the angle of incidence.

-The endoscope is used to see inside the body of a patient without cutting it open and is…


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