OpenStax College Physics for AP® Courses, Chapter 24, Problem 3 (Test Prep for AP® Courses)

This is College Physics Answers with Shaun Dychko. So this is not the best question because there are multiple answers. So anyway let's talk about it. So a wave is traveling through medium until it hits the end of the medium and there's nothing but vacuum beyond. What happens to a mechanical wave, such as sound or spring? And what happens to electromagnetic wave? When electromagnetic wave can carry on and so you know A, C or D are possibilities. But an electromagnetic wave also would be reflected as well. Because whenever light hits a boundary between media, it will partially get reflected and partially transmitted. But anyway, predominately depending on the angle of incidence, I suppose, it would continue on but it's not really clear actually what happens. I mean strictly speaking, you know, if you're in a swimming pool and you look upwards at the water from below, you can see that there is a certain angle called the critical angle beyond which none of the light is transmitted at all. So light will go from the floor of the pool and it will reflect completely off the surface and then reach your eye and none of it gets transmitted. So this continuing on business is not strictly true but it's I suppose the best answer. Mechanical wave definitely cannot continue on and there's no reason for it to stop. It can't continue on because there is nothing. It requires a medium to propagate through and so like there's a vacuum and so there's nothing there for it to go through. So it can't continue on. There's no reason for it to stop either because you know it is still energy there and something has to happen to it and so it is going to get reflected backwards. And the best answer then is A.