Question

Problem 6 A screen is placed a distance R = 10m away from a 2-slit setup. Point P on the screen is a point located 180 mm from the central maximum. The distance between slits is d = 0.1mm. A laser beam is incident on the slits from the left, as shown. With this setup the third bright spot in the interference pattern is exactly at point P. (a) [3 points) Calculate the wavelength of the laser. (b) [3 points) Determine the phase difference between the rays at a point on the screen 140 mm from the central max. (c) (2 points) Determine the intensity of the light at a point on the screen 140 mm from the central max. Express your answer as a percentage of the intensity of the central max Io.

Answer 1

Given la) R=lom dzo.lmm 20.1x10-3 m Location of P 2 180mm Location of third bright, u= 32 Yo dietanu of paint from central maxima 180 X 10 -12 3X10 XA O.1X10-3 ANSWER 107m 6 x da 18dx10-7 - 2 30 (b) Path difference (An)= red) = 140810*10-4 140x10om 10 2 14x10-7m (c) Intensity at any point is giran by = 450 Cel? (EI AN) = 450 cop" ( 7 / g * 14X107) 245664 (79) - 4F COR? (25+5) 2450 God? 7 2 1920 x 17 2 3 = 320

(d) Intensity due to differaction In to sin? [Tay] Trama de 7 sint (axlotx 140 X163 ) 6X207x18 (axlo-exilio X10-312 6x10-7x10 - To Sinh L 77 78 Tog - TESAL 0.005 To 0.5% of die to