Question

a) An oil slick on water is 108 nm thick and illuminated by white light incident perpendicular to its surface. What color does the oil appear (what is the most constructively reflected wavelength, in nanometers), given its index of refraction is 1.41? (Assume the index of refraction of water is 1.33.)

wavelength________ nm

b)A ruby laser beam is reflected from the surface of a CD onto a wall. The brightest spot is the reflected beam at an angle equal to the angle of incidence. However, fringes are also observed. If the wall is 1.1 m from the CD, and the first bright fringe is 0.546 m from the central maximum, what is the spacing (in m) of grooves on the CD? (Assume a ruby laser has a wavelength of 694 nm. Also assume that the main reflected beam incident on the wall is exactly perpendicular to the wall.)

__________m

c) A diffraction grating has 2,230 lines per centimeter. At what angle in degrees will the first-order maximum be for 555 nm wavelength green light?

Answer 1

(a) The condition for constructive interference is (m + 12 ) x t court 2 mao,1,2. . - 2 hoil do txanine 108nm x 2x1.41 (m+1) > x= 609.12 hm²60.9 hm (orange wlow) (6) The condition for bright fringes yzmXD - da mxo d >dz 1x 694x109x 1.1 y 1-398x100m 0.546 = d z 1:398 mm e ) The condition for marima is el sin oz mi. N 223000 da ! (223/102) On sin! ( 1x 555xlox 2.23000) 0 7.11