Medical Applications

1. Part of the electromagnetic spectrum, short wavelength and cause ionisation.
   1. Precautions need to be taken.
2. Are used to diagnose and treat some conditions.
   1. CT scans, bone fractures, dental problems and killing cancer cells.
3. They are absorbed by bone and metal, but transmitted by healthy tissue.

1. Systems produce ultrasound waves, which have a frequency higher than what the human ear can hear.
   1. 20Hz to 20,000Hz
2. Waves are partially reflected when they meet a boundary between two different media.
   1. The time taken can be used to work out the distance.
3. Distance = speed * time
   1. s = v * t
4. Examples are pre-natal scans and removing kidney stones.

Annotations:

• [Image: http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/imggo/focalength.gif]

1. Refraction is the change of direction of light.
   1. A lens forms an image by refracting light.
2. Distance from lens to the focal point is the focal length.