Consider an electric dipole with charge +qlocated at xd, and charge -q located at x+d. (a) compute the electric field e(0, y, 0) for points on the y-axis. justify the direction (sign) of your answer by sketching the field lines of the dipole. examine the limiting case where the dipole is very far away from our point of interest (i. e. y> > d) by writing your answer in terms of a simple formula times a power series in the small quantity d2/y2 (keeping terms through 2nd order).

The frequency of a tuning fork can be found by the method shown. a long tube open at both ends is submerged in a beaker of water, and the vibrating tuning fork is placed near the top of the tube. the length l of the air column is adjusted by moving the tube vertically. the sound waves generated by the fork are reinforced when the length of the air column corresponds to one of the resonant frequencies of the tube. the smallest value for l for which a peak occurs in sound intensity is 7 cm. l what is the frequency of the tuning fork? the speed of sound in air is 345 m/s. answer in units of hz