ultrasound+waves

Ultrasound waves
The principle of ultrasound has been copied to the nature. Bats use it for orientation and hunting. The animals send out sound waves with a frequency of 40 up to 90 MHz, a frequency humans cannot hear. In this way they are able to locate their food.

In medicine ultrasound is used too. Waves with a frequency of two to twelve MHz in short pulses are sent into the body. The skin reflects the wave, which is recorded and transformed to an electrical signal, these can converted by a computer into a video, called sonogram, which you can see on a monitor. You can use it to see the fetus growing up, if a woman is pregnant, to identify cancer, so you can help the patient and to analyze heart diseases. You also can break stones of mineral in little pieces. Ultrasound cannot be used to examine bones.

The site I got the applet from is one, which engineers from [|the company EDT] designed. These engineers check how flexible a material is by applying ultrasound. For example if they want to check how hard the cover of your computer is, they can check it easily without any damage to it. Only because of ultrasound.

At this [|applet] you can change the frequency, the numbers of nodes (where the waves come from), the focal length (there you can choose the background), the medium and it also shows you how fast the sound travels. You can play around with the transducer width, which seems to have an impact on how the wave is reflected. I prefer using one node at a frequency of 5Mhz ( because then you can see the wave in a very clear way), but just try.