## 20120309

### Physics quiz question: double slit interference

Physics 205B Quiz 3, spring semester 2012
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 25.49

A double slit is illuminated with monochromatic light of wavelength 540 nm. The m = 0 and m = 1 bright fringes are separated by 3.2 mm on a distant screen 4.0 m from the slits. (Consider the small-angle approximation to be valid.) The path difference between the light from each slit that reaches the m = 1 bright fringe is:
(A) 0.
(B) 270 nm.
(C) 540 nm.
(D) 1.6 mm.
(E) 3.2 mm.

For monochromatic light passing through double slits, the path length difference to the constructive interference bright fringes must be an integer number of wavelengths. The m = 0 bright fringe will have a path length difference of 0, while the m = 1 bright fringe will have a path length difference of one whole wavelength, or 540 nm.

Section 30882
Exam code: quiz03gR7L
(A) : 1 student
(B) : 3 students
(C) : 10 students
(D) : 5 students
(E) : 8 students

Success level: 37%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.86