X-rays are part of the electromagnetic spectrum. They have a high frequency and a very short wavelength. They affect a photographic film in the same way as light and they are absorbed by metal and bone. They are transmitted by healthy tissue.
X-rays are used to form images of bones on photographic film to check for fractures and dental problems. Charge-coupled devices (CCDs) can be used to form electronic images of X-rays. CT scanners use X-rays to produce digital images of a cross-section through the body. Some body organs that are made of soft tissue, such as the intestines, can be filled with a contrast medium that absorbs X-rays. They can then be seen on an X-ray image.
However, X-rays cause ionisation and can damage living tissue when they pass through it. Workers should wear film badges and when possible use lead screens to shield them from the X-rays. X-rays can also be used for therapy. They can be used to treat cancerous tumours near the body surface. So although X-rays can cause cancer, they can also be used to treat it.
The human ear can detect soundwaves with frequencies of between 20-20,000 Hz. Sound waves of a higher frequency are called ultrasound waves. Electronic systems can produce ultrasound waves. When a wave meets a boundary between two different materials, part of the wave is reflected back. The wave travels back through the medium to a detector. The time it takes to reach the detector can be used to work out how far away the boundary is. The results can be processed by a computer to produce an image.
The distance travelled by an ultrasound wave can be found using the equation:
s = vt, where s= the distance travelled in m, v= speed of the ultrasound wave in m/s and t is the time taken in s.
In the time between the transmitter sending out…