During an ultrasound scan, an air gap between the probe and skin produces a strong echo and a poor image of deeper tissues. Adding gel reduces this echo and improves the image.
Which explains the improvement?
More ultrasound is reflected at the surface, so more enters the body.
Less ultrasound is transmitted at the surface, so deeper echoes increase.
More ultrasound is absorbed at the surface, so deeper echoes increase.
Less ultrasound is reflected at the surface, so more enters the body.
112 exam-style questions on Edexcel GCSE Physics 4.3 Sound, ultrasound and infrasound, covering 4.3.1 Sound waves, vibrations and the human ear, 4.3.2 Ultrasound and infrasound, 4.3.3 Uses of ultrasound and infrasound, and 4.3.4 Sound waves passing between media. Each one has a worked solution and a mark scheme showing where the marks go.