Physics 205A Quiz 1, fall semester 2016
Cuesta College, San Luis Obispo, CA
The Wien displacement constant b is given by the expression[*]:
b = h·c/k.
The Planck constant h is measured in units of kg·m2·s–1, the speed of light c is measured in units of m·s–1, and the Boltzmann constant k is measured in units of K–1·kg·m2·s–2. The units for the Wien displacement constant b are:
(A) K·m.
(B) K–1·s–1.
(C) K·kg·m–1.
(D) K–1·m4·s–4.
[*] wki.pe/Physical_constant#Physico-chemical_constants.
Correct answer (highlight to unhide): (A)
Starting with the expression for the Wien displacement constant b:
b = h·c/k,
and replacing the quantities in the equation with their K, kg, m and s units, the units of b are:
b = (kg·m2·s–1)·(m·s–1)/(K–1·kg·m2·s–2),
b = (kg·m3·s–2)/(K–1·kg·m2·s–2),
b = K·m.
Sections 70854, 70855, 73320
Exam code: quiz01bIR6
(A) : 53 students
(B) : 2 students
(C) : 0 students
(D) : 2 students
Success level: 93%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.15
Showing posts with label fine structure constant. Show all posts
Showing posts with label fine structure constant. Show all posts
20160904
Physics quiz question: fine structure constant units
Physics 205A Quiz 1, fall semester 2016
Cuesta College, San Luis Obispo, CA
The Rydberg constant R∞ (measured in units of m–1) is a physical constant used in spectroscopy[*]:
R∞ = α2·me·c/(2·h).
The electron mass me is measured in units of kg, the speed of light c is measured in units of m·s–1, and the Planck constant h is measured in units of kg·m2·s–1. The units for the constant α are:
(A) kg1/2·m3/2.
(B) m2·s–1.
(C) kg·m·s.
(D) (No units, as it is a dimensionless quantity.)
[*] wki.pe/Rydberg_constant#Alternative_expressions.
Correct answer (highlight to unhide): (D)
The constant α can be expressed as:
α = sqrt(2·h·R∞/(me·c)),
and replacing the quantities in the equation with their kg, m and s units, the units of α are:
α = sqrt((kg·m2·s–1)·(m–1)/((kg)·(m·s–1))),
α = sqrt((kg·m·s–1)/(kg·m·s–1)),
α = sqrt(1);
thus making α a dimensionless quantity.
Sections 70854, 70855, 73320
Exam code: quiz01bIR6
(A) : 11 students
(B) : 14 students
(C) : 6 students
(D) : 26 students
Success level: 46%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50
Cuesta College, San Luis Obispo, CA
The Rydberg constant R∞ (measured in units of m–1) is a physical constant used in spectroscopy[*]:
R∞ = α2·me·c/(2·h).
The electron mass me is measured in units of kg, the speed of light c is measured in units of m·s–1, and the Planck constant h is measured in units of kg·m2·s–1. The units for the constant α are:
(A) kg1/2·m3/2.
(B) m2·s–1.
(C) kg·m·s.
(D) (No units, as it is a dimensionless quantity.)
[*] wki.pe/Rydberg_constant#Alternative_expressions.
Correct answer (highlight to unhide): (D)
The constant α can be expressed as:
α = sqrt(2·h·R∞/(me·c)),
and replacing the quantities in the equation with their kg, m and s units, the units of α are:
α = sqrt((kg·m2·s–1)·(m–1)/((kg)·(m·s–1))),
α = sqrt((kg·m·s–1)/(kg·m·s–1)),
α = sqrt(1);
thus making α a dimensionless quantity.
Sections 70854, 70855, 73320
Exam code: quiz01bIR6
(A) : 11 students
(B) : 14 students
(C) : 6 students
(D) : 26 students
Success level: 46%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50
Subscribe to:
Posts (Atom)