Re: How can you break glass by simply singing?

Hi Anson
In this case TV has not been lying to you, you are right about the 
resonation thing: Glass will break given a sound wave of the right 
frequency and with enough energy. To do this, open your mouth and 
try and make a sound at the resonating frequency of glass (i’m not 
sure what this is) preferably a perfect sine wave. Or use a signal 
generator attached to a speaker. (oh and be careful, broken glass is 
quite problematic to get out of someone else’s skin).
Resonance works by certain objects / materials having specific 
frequencies which they will respond to. If you have a wave arriving at 
an object and the wave is at the correct frequency for the object to 
resonate, it will start to vibrate. This gives the object more energy and 
a possible result of this is chemical bonds breaking, and so the 
glass shatters. This is the same principle by which microwave ovens 
work. They emit electromagnetic radiation at the resonant frequency 
of water and cause it to heat up. (again careful, keep the microwave 
door closed when its on, most have a safety mechanism. But if you 
cook something and leave it open, you turn into a mobile phone user)

One thing i thought i should mention, as it is kind of related to this is 
the Casimir effect. I’m not sure how old grade 7-9 is, as i’m from the 
UK, but this is mainly quantum theory type stuff and could be new to 
you (although i hope its not!). It basically goes like this: the uncertainty 
principle allows energy / matter be created in a vacuum, and it almost 
always disappears soon after. However, add a pair of metal plates 
facing each other, particles created will ‘bounce’ between them. If you 
have a photon between the plates, it can only have wavelengths 
which are integral fractions of the distance between the plates. And 
so the probability of particles being created between the plates is 
less than that outside the plates, as any wavelength can exist 
outside. What now happens is an effective pressure difference is 
made, and so the plates move together, as there is are less particles 
per unit volume between plates. This, unlike the mobile phone thing 
above, is true, and has been tested. Also, if you have a energetic 
particle, like a radioactive nucleus, between the plates, it is unable to 
loose energy (decay) by emitting, say,  a photon which is not of 
wavelength with an integral fraction of the distance between the 
plates. If it does release particles of the correct wavelength it will 
decay faster (apparently).
If you can somehow fit this into your science report, it should baffle 
and perplex the teacher, and good times will be had by all. Oh and 
make sure you understand it a bit, ‘cause otherwise that would be 
cheating.
links / books (possibly relevant):
i can’t think of any links of the top of my head, but search 
www.Googol.com, this seems really fast and hasn’t failed me yet (i’m 
not getting paid to say that btw). Same with books, just look for them 
in shops (or online) its good to find ones you feel comfortable using.

there y’go then, hope it ws useful
Paul Henderson