Explain how defects in a metal block can be detected using ultrasound.
Answer
Metal blocks are used in building bridges, machines etc
Sometimes, these metal blocks look fine from outside but may have cracks inside
To detect it, ultrasound waves are passed
If there is no defect,these ultrasound waves pass through and are detected by detectors
But if there is a defect, these waves reflect back (and hence not detected by detector).