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There are three boxes and one has a prize inside. You are told to choose a box. One of the other boxes is then opened, showing that it is empty. You are given the option to switch your choice to the other remaining box. Should you switch? Why?

Let's think of the three boxes as A, B and C. Say we choose box A. There is a 1 in 3 chance that our box has the prize inside, and so a 2 in 3 chance that it does not. When a box is opened and shown to be em...
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Answered by David A. • Maths tutor
14864 Views

What determines the acoustic impedance of a material and why is it useful in understanding ultrasound imaging?

Acoustic impedance is the density of a material multiplied by the speed of sound in the material. Knowing these two values allows use to calculate how much of the sound energy is reflected at an interface be...
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Answered by David A. • Physics tutor
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How is a piezoelectric crystal used to generate waves of ultrasound?

A piezoelectric crystal makes use of the peizoelectric effect . This is the production of a voltage when mechanical stress is applied across the material. This occurs only in materials when the unit cells wh...
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Answered by David A. • Physics tutor
11315 Views

How do I answer an evaluation question?

E.g. Evaluate how would a fall in interest rates effect economic growth.Start by defining the key terms - economic growth, possibly interest rates very briefly.Draw a diagram showing Aggregate Demand shiftin...
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How can I dissect a written source in exam conditions?

It's completely understandable to be a little apprehensive about having to engage higher-level analysis of sources under time pressure, but don't worry! There are several steps you can take to help you get i...
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Answered by Elsa M. • History tutor
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