I believe the answer is Microwaves (just to clarify, not the oven). They're widely used for communications.<span />
A microwave uses heat waves that keeps in side the machine to heat up the cup of water
Hope this helps :)
<span>(a) Consider the system consisting of the child and the disk, but not including the ... (g) What was the speed of the child just after the collision? ... ends up standing at a new location a distance R/2 = 0.95 mfrom the axle. Now what is the angular speed? (It helps to do this analysis algebraically and plug innumbers at the end.)</span><span>
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E concave mirror because it reflects the light