The two-dimensional square lattice has ai ae, and a2 aéz. 1. show that the reciprocal lattice is also square. 2. use the following recipe for finding the first three brillouin zones: the b8z is obtained by starting at any reciprocal lattice point (which is then the origin) and constructing vectors to all neighbouring reciprocal lattice points. lines are then constructed perpendicular to and passing through the midpoints of these vectors. the bz is the cell with the smallest area about the origin bounded by these lines. the 2nd b2 is the area between the 1t bz and the next smallest closed polygon formed by the lines. similarly for the 3" bz.

Askydiver weighing 140 lb (including equipment) falls vertically downward from an altitude of 19,000 ft and opens the parachute after 18 s of free fall. assume that the force of air resistance, which is directed opposite to the velocity, is of magnitude 0.55|v| when the parachute is closed and is of magnitude 14|v| when the parachute is open, where the velocity v is measured in ft/s. assume that acceleration due to gravity has magnitude 32 ft/s/s; remember that weight is the product of mass and gravitational acceleration. (a) find the speed of the skydiver when the parachute opens. (b) find the distance fallen before the parachute opens. (c) what is the limiting velocity vl after the parachute opens? (d) determine how long the sky diver is in the air after the parachute opens. (e) plot the graph of velocity versus time from the beginning of the fall until the skydiver reaches the ground.

Which object is most likely represented by a dot?

How many times did thomas edison mess up the light bulb