# Modern Physics-HELP 911!

by kizersi5
Tags: modern, physicshelp
 HW Helper P: 1,449 A monochromatic beam (1) entering from the left splits up at B, a half silvered mirror, into two beams (2) and (3) and is reflected back by two mirrors. Beam (2) continues onwards to O and on its return (3) is reflected downward also to O (part of both beams actually since the mirror is half silvered). At O the beams are combined optically resulting interference of the two beams. If the paths of the two beams , (2) and (3), are the same length constructive interference will result at and a bright fringe will be observed at O. If the movable mirror is moved $\frac{\lambda}{4}$ closer to the beam splitter this condition will change to destructive interference. If the mirror is moved by $\frac{\lambda}{2}$ one fringe change will be observed at O. This gives you your first equation.