Engineers use ultrasonic transducers to test for internal flaws in steel structural columns. The transducer placed against the column vibrates 25 million times per second.
(i) State the frequency of the ultrasound waves produced and give the unit.
(ii) Suggest how these ultrasound waves are used to detect internal cracks or voids in the column.
(iii) Suggest why a viscous couplant gel is applied between the transducer and the steel column.
Ultrasound waves are also used in marine sonar systems to map the topography of the seabed.
(i) A sonar image of the seabed is formed by waves which bounce off the boundary between the water and the sea floor. This is an example of waves that are: A. refracted B. diffracted C. reflected D. absorbed
(ii) State the equation linking wave speed, frequency, and wavelength.
(iii) In seawater, sonar ultrasound waves travel at a speed of 1530 m/s1530\text{ m/s}1530 m/s and have a wavelength of 0.00018 m0.00018\text{ m}0.00018 m. Calculate the frequency, in MHz\text{MHz}MHz, of these ultrasound waves.
Other waves also have structural imaging uses. High-energy gamma rays are used to inspect thick welds in industrial metalwork. Suggest two differences between ultrasound waves and gamma rays.
