Aphysicist lost in the mountains tries to make a telescope using the lenses from his reading glasses. they have powers of 1.5 d and 4.0 d , respectively. what maximum magnification telescope is possible?
which lens should be used as the eyepiece?

photocells convert light energy to electricity

no. dot product   =0 when vecs at right angles

it doesn't. it was imagined up in the middle ages.

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me