Question

how are multiple reflections helpful to doctors and engineers

Answer 1

stethoscope is a medical instrument used for listening to sounds produced within the body  chiefly in heart or lungs.in stethoscope the sound of the patients heart beat reaches the doctors ears by multiple reflection and by amplifying sound.
generally the ceilings of concert halls, conference hall and cinema halls are designed such that sound after reflection reaches all corners of the hall . in some halls a curved ceiling is arranged in such a way that the sound after reflecting from ceiling spreads evenly across the hall.

Hope it helps....

Answer 2

Explanation:

Pure calcium carbonate can be produced from marble, or it can be prepared by passing carbon dioxide into a solution of calcium hydroxide. In the later case calcium carbonate is derived from the mixture, forming a grade of product called "precipitated calcium carbonate,” or PCC.