Physics Revision - Ultrasound

KEY FACTS ABOUT ULTRASOUND:

• Above human hearing range - above 20,000 Hz or 20 KHz
• Higher Frequency
• Produced by electronics
• Its used for ultrasound scans - pre natal (pregnancy) - used 'safe' (rather than X-Rays)
• All about reflection
• Partially reflected when they meet a boundary between two different layers of 'flesh' (soft tissue/bone)
• It works by: 1. Dectector measures time between reflections, 2. Work out how far away it is and builds up a picture electronically
• Used on injuries
• When an ultrasound is carried out between ultrasound 'pad' and skin - gel used, this helps ultrasound to 'enter' the body and not reflect off.
• Used for dental cleaning, the removal of kidney stones and jewllery cleaning --> vibrations caused by ultrasound break up the dirt or kidney stones by concentrating high energy waves at them.
• EQUATION: DISTANCE BETWEEN INTERFACES (LAYERS) = SPEED× TIME TAKEN
• NOTE : speed of waves × time taken = distance