Noise-canceling headphones are an application of destructive interference. each side of the headphones uses a microphone to pick up noise, delays it slightly, then rebroadcasts the noise next to your ear where it can interfere with the incoming sound wave of the noise. suppose you are sitting 1.8 m from an annoying, 200 hz buzzing sound.

what is the minimum headphone delay, in ms, that will cancel this noise? (the answer isn't t = 1/f is something i'm missing here as the answer isn't 5ms)

Explain why electric current cannot exist if a current doesn't have a voltage source.

A15.75-g piece of iron absorbs 1086.75 joules of heat energy, and its temperature changes from 25°c to 175°c. what is the specific heat capacity of iron?

Materials will have different energies associated with the electrons inside them. this is related to how strongly bound they are by their work function. if we sandwich a material with a very low energy between two materials with a high energy, we create a trap for an electron. if this trap is very narrow in one direction in comparison to the others, this is approximately a 1-dimensional box that confines the electron. what is the lowest energy of an electron in the box if the thinnest direction across the materials is 4.81 nm?