Hi Gary the thin film of soap is interesting a way of seeing the U..S beam i haven,t seen that before .
I have been stuck not on the Ultrasonic side but the polygon laser mirror monitor side of things since i don't have a spare laser printer mirror at the moment ..
as you saw in the last post i had made one out of of steel nuts and little mirrors ...i like the motor i was going to use but i think the shaft at the end is a little bent or the pulley thing on it i am using as the base , does not take much to send a laser beam off track ..
So apart from this i have been looking into polygon or multiple shapes to reflect the laser ...some of the polished nuts are not to bad which would do away with the mirrors .
What i have found is even with the best i have a which is a 4 sided high polished steel door stopper, metal mirrors defocus at distance not so much a problem for this one but of cause less sides it has higher speed you need to rotate it ...The best shape i have found handy is our 50 cent coin 12 sides...if i learn how to polish coin to a mirror finish this could come in handy ..
But i think for now i will stick with a polished nut or again one with mirrors and try again with a different motor ///
Been a bit like make it test it pull it to bits try again.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.