Download Midterm 1 - UF Physics

Name:_______________________
PHY3101
2-16-00
Midterm 1
Closed book exam. One 8.5x11" study sheet is allowed. A calculator is allowed also.
Exam is worth 30 points, 15% of your total grade.
h = 6.6261 × 10 −34 J-s
h = 4.1357 × 10 −15 eV-s
hc = 1240 eV-nm
× 10−34 J - s
h = h / 2π = 10546
.
h = 6.5821 × 10−16 eV - s
me = 9.11 × 10 −31 kg
c = 3.0 × 108 m/s
λf = c
Eγ = h f
λ=h/p
1 Watt = 1 J/s
mp = 1673
.
× 10 −27 kg
me = 0.511 MeV / c2
mp = 938.3 MeV / c2 mµ = 105.7 MeV / c2
1 light-year = 0.946 × 1016 m
1 year = 316
. × 107 s
e2
= 144
. × 10−9 eV - m
4πε 0
F = q(E + v × B )
W = qV
b g
t ′ = γ ct − vx / c h
y′ = y
z′ = z
γ =
x ′ = γ x − vt
1
1 − v 2 / c2
2
L0
γ
ux ′ =
t = γ t0
L=
E = γmc 2
E K = γ − 1 mc 2
f =
b g
1± v / c
f0
1m v / c
p = γmu
uy ′ =
uy
vu
γ 1 − 2x
c
FG
H
IJ
K
F = dp / dt
m2 c 4 = E 2 − p 2 c 2
a0
Z2E
En = − 2 0
Z
n
2
4πε 0 h
a0 =
= 0.53 × 10 −10 m
2
me
E
R∞ = 0 = 109737
.
× 107 m-1
hc
1
1
1
= Z2R 2 − 2
λ
nl nu
rn = n2
F
GH
ux − v
vu
1 − 2x
c
e = 16022
.
× 10−19 C
1 eV = 16022
.
× 10−19 J
1 MeV = 106 eV
1 nm = 10−9 m
1 MHz = 106 s-1
mµ = 1881
. × 10−28 kg
I
JK
λ m T = 2.898 × 10 −3 m - K
e 4 me
= 13.6 eV
2h 2 (4πε 0 ) 2
E
RH = 0 = 109678
.
× 107 m-1
hc
1
1
1
=
+
µ me mN
E0 = −
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eV0 = hf − φ
Name:_______________________
PHY3101
2-16-00
1. The distance to the nearest star, as measured by astronomers on Earth, is
4 light-years. Suppose that you are in a starship traveling at a constant velocity of
97% of the speed of light toward this star.
(a) [3 points] How long does the trip take from Earth to the star according to you
on the starship?
(b) [3 points] At what frequency will Mission Control on Earth receive your
transmissions during the outbound journey if the transmission in the rest
frame of the starship is at a frequency of f = 4 GHz (4000 MHz) ?
Page 2 of 5
Name:_______________________
PHY3101
2-16-00
2. A particle is measured to have a total energy of 918 MeV and a momentum of
500 MeV / c.
(a) [3 points] What is the mass of the particle?
(b) [3 points] What is the velocity of the particle?
3. [4 points] Determine the maximum kinetic energy of an electron ejected from a metal
plate of aluminum (work function φ = 4.08 eV ) when exposed to ultraviolet light
with a wavelength of 254 nm.
Page 3 of 5
Name:_______________________
PHY3101
2-16-00
4. [4 points] How many photons per second are emitted from the antenna of an FM
radio station that transmits 1000 W of power at a frequency of 100 MHz? What is the
wavelength of the electromagnetic radiation?
5. [4 points] Determine the wavelength of the missing line in the following series from
the emission spectra of hydrogen: 1876 nm, 1282 nm, ???, 1005 nm, …
Page 4 of 5
Name:_______________________
PHY3101
2-16-00
6. [4 points] A doubly-ionized lithium ion (Li++) in the ground state absorbs a photon
with a wavelength of 11.4 nm. Determine the principal quantum number n of the
excited state the atom jumps to after the absorption.
7. [2 points] Describe how classical physics fails to explain any one of the following
phenomena, and what solution was proposed: Black-body radiation, the photoelectric
effect, or the light emission from atoms.
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