Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 22.19(a)
Parent Géry
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Light of wavelength 218 nm in arsenic trisulfide (As2S3) (index of refraction[*] of 2.66) is incident at the interface between arsenic trisulfide and air (index of refraction 1.000). The wavelength of this light in air is:
(A) 82.0 nm.
(B) 218 nm.
(C) 362 nm.
(D) 580 nm.
[*] nvlpubs.nist.gov/nistpubs/jres/59/jresv59n2p83_A1b.pdf.
Correct answer (highlight to unhide): (D)
The relations between the index of refraction and the speed of light, for arsenic trisulfide (medium 1) and for air (medium 2) are:
n1 = c/v1,
n2 = c/v2,
where the given (or assumed to be known) quantities, unknown quantities, and quantities to be explicitly solved for are denoted. Also the relations between wavelength, speed, and frequency are:
λ1 = v1/f1,
λ2 = v2/f2.
However, the frequency of the light in arsenic trisulfide is the same as the frequency it has in air, such that:
f1 = f2,
(v1/λ1) = (v2/λ2),
λ2 = λ1·(v2/v1),
λ2 = λ1·((c/n2)/(c/n1)),
λ2 = λ1·(n1/n2) = (218 nm)·(2.66/1.000) = 580 nm.
(Response (A) is (218 nm)/(2.66); response (C) is (218 nm)·(1.66).)
Section 30882
Exam code: quiz01b3Es
(A) : 6 students
(B) : 3 students
(C) : 4 students
(D) : 21 students
(No response) : 1 student
Success level: 60%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.91
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