81 SSM Figure 29-84 shows a cross section of an infinite conducting sheet carrying a current per unit x-length of 2; the current emerges perpendicularly out of the page. (a) Use the Biot-Savart law and symmetry to show that for all points B •P x B P'. Figure 29-84 Problem 81. P above the sheet and all points P' below it, the magnetic field B is parallel to the sheet and directed as shown. (b) Use Ampere's law to prove that B = ½µλ at all points P and P'.

(λvacuum =640nm) red light (λ vacuum = 640 nm) and green light perpendicularly on a soap film (n=1.31) A mixture of (a vacuum = 512 nm) shines that has air on both side. What is the minimum nonzero thickness of the film, so that destructive interference to look red in reflected light? nm Causes it

Suppose the inteference pattern shown in the figure below is produced by monochromatic light passing through a diffraction grating, that has 260 lines/mm, and onto a screen 1.40m away. What is the wavelength of light if the distance between the dashed lines is 180cm? nm