ESDU Challenge: Shock Wave

I'll buy a B and a G, Vanna.

I'm not Vanna. I only sell bowels, as in these challenges.

I am in! What about Vanna?

As far as I know, she is still on "Wheel of Fortune", where contestants guess letters that fill in some phrase or title. The contestants can "buy" vowels to help this fill-in scheme. Her official IRS occupational title is "letter turner", but I forget the 4-digit code for it. I doubt we are each other's type, but she is major cool, and would probably be a conversational blast.

Question a) is a bit vague. The speed of the shock wave in water is the same as the speed of any sound in water, which is about 4 times faster than the 'speed of sound' in air.

There is no change in 'impedance' of the water in the pipe, so I don't see why there would be a reflection. There will be some diffraction from the edges of the pipe, as there is anytime a wave encounters a boundary; but diffraction is not physically the same as reflection. So I'd say b) is false.

Using my experience with fiber optics, I'd say that aside from my comments on a) and b), the only one I believe is true exactly as stated is g).

Yeah, that was worded a little vaguely, but I think that A also is true.

Tsunamis do the same thing. The actual physical wave you see on the shore is a byproduct of the tsunami.

I am going to argue against you on B. Sort of... While it is technically refraction (at least predominantly), you still get a wave front from that diffraction that travels not only backward, but in all directions from the mouth of the tube edge.

This is a case where the wording is not technically correct, perhaps the were asking if the small inlet would provide a reflection, which it will not. However, the edges will (to a small degree) and diffraction will as well to a larger degree.

I agree with you on g. The velocity of the shock wave will not change, but the amplitude will!

More about b): It's not really refraction, since there is no change in the medium. You get refraction of light (for ex.) passing from air to water, or water to glass, and so forth. The diffraction at the boundary will create ripples that travel in all directions, that's true. But I'm sticking with my comment that the phenomenon is not, per se, a reflection.

This is assuming that the pipe has a fairly large diameter. It the pipe opening was smaller than the effective wave pulse then yes, it would reflect, just as the metal mesh in the window of a microwave oven reflects the microwaves.

No, refraction can be caused when a layer that a wave is propagating against changes direction.

A great example is the corner of a speaker cabinet where the sound wave suddenly crosses the corner a refraction wave is created. Refraction can be quite noticeable and in the case of the speaker cabinet it will interfere with the performance of the sound.

Even a slit where a wave travels through will cause refraction. Try it in a bath tub, or remember the double slit experiment with light?

Remember, we're talking a "shock wave" here, which have decidedly different qualities than normal waves.

I'll buy a) and g)

And say that a shock wave will be reflected directly back from the shore only if the shore is vertical. Otherwise it will be reflected at some angle, depending on the angle of incidence.

The resulting shock wave will indeed be reflected in all directions away from the wall (think doughnut) so would move vertically across the pipe opening as well.

Baboom....

https://www.youtube.com/watch?v=5s3-c2gpbEs

OK, I'm not afraid to show my ignorance in public. So I'm gunna say a., d., and e., are true.

So much for pride.