Explain how defects in a metal block can be detected using ultrasound.

(N/A) Ultrasound can be used to detect cracks and flaws in metal blocks.
$1$. Ultrasound waves are allowed to pass through the metal block,and detectors are used to detect the transmitted waves.
$2$. If there is even a small defect,such as a crack or a hole inside the metal block,the ultrasound waves get reflected back from the defect site.
$3$. This reflection indicates the presence of a flaw or defect in the metal block.
$4$. Since ultrasound has a high frequency,it can travel through the material and detect internal defects that are not visible from the outside.