Physics quiz question: double slit spacing

Physics 205B Quiz 3, spring semester 2016
Cuesta College, San Luis Obispo, CA

A red laser (wavelength 632 nm) illuminates two slits, producing a first maximum located at angle of 27° on a screen located 1.75 m away. The two slits are spaced __________ apart.
(A) 0.29 µm.
(B) 0.70 µm.
(C) 1.1 µm.
(D) 1.4 µm.

Correct answer (highlight to unhide): (D)

The first maxima angle θ for double-slit (and grating) interference is given by relation:

d·sinθ = m·λ,

where m = 1, such that:

d = λ/sinθ = (632×10^–9 nm)/sin(27°) = 1.39209...×10^–6 m,

or to two significant figures, 1.4 µm.

(Response (A) is λ·sinθ; response (B) is λ/(2·sinθ); and response (C) is λ·L.)

Sections 30882, 30883
Exam code: quiz03Ccf7
(A) : 0 students
(B) : 4 students
(C) : 4 students
(D) : 32 students

Success level: 80%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.11