Q. Coherent light with wavelength 592 nm passes through two very narrow slits, and the interference pattern is observed on a screen a distance of 3.00 {rm m} from the slits. The first-order bright fringe is a distance of 4.84 {rm mm} from the center of the central bright fringe.
Q. A window washer pushes his scrub brush up a vertical window at constant speed by applying a force. The brush weighs 14.2 N and the coefficient of kinetic friction is 0.150.
Calculate the magnitude of the force .
Calculate the magnitude of the normal force exerted by the window on the brush.