Acoustics Answers

what are shock waves and sonic boom

what are five basic condition for good acoustic of a concert hall

hello,
see, none of the books have been explicit about this so I wanted to clarify my theory,
so what I want to ask is,
when a person wears a eyeglass for say myopia, he is correction his lowest accomidation by adding a negative power,? for example,
a person has the farthest point 100 cm,
so his power (in current state) would be =
100*(1/100+10/25) = 41D . now to see objects at say infinity, we must have power 40D(we know that) so, the power of the lenses should be 40D-41D = -1D. ? I mean so that when an object is at infinity, it will create a virtual image at 100cm (the farthest point of the eye) and from there the eye would be able to focus it, with the power 41D only? so what i mean to say is that a corrective lens corrects the accomodation of an eye(which is between 40D - 44D)? plus whenever a object is placed say nearer to than infinity but more than the farthest point, say 500cm,first the corrective lens makes a virtual image (at a distanc < 100 cm) and then our eye will adjust the focal length. and thus the power should be > 41 D(cause that's the lowest that eye can go upto)
and I see that when we subtract -1D (power of lense) frying the power to focused this virtual image, I find its equal to the power an eye without myopia would needy to focus the object at 500 cm. so Am I right?

plus one more query,
how can we look at closer objects clearly while wearing glasses to look at distant things!
please reply
thank you

how does increase in temperature affect the velocity of sound in water.
Does it reduces, increase or increase and reduce at a point and why that phenomenon

We know when two similar waves moves in opposite directions and interfere, a standing waves is produced. So when a sound wave enters a pipe, it will produce a standing wave with the reflected sound wave. Is standing wave always produced in the pipe regardless a loud sound(resonance) is herd or not?

15.0 meters from a sound source that radiates freely in all directions, the intensity is 0.00480 W/m2. What is the rate at which the source is emitting sound energy?