Cheung, Anthony – Homework 2 – Due: Sep 19 2006, midnight – Inst: McCord
1
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printout
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001
(part 1 of 1) 10 points
The work function for chrominum metal is
4.37 eV. What wavelength of radiation must
be used to eject electrons with a velocity of
9300 km
/
s?
Correct answer: 4
.
95788 nm.
Explanation:
v
= 9300 km
/
s = 9
.
3
×
10
6
m
/
s
The wavelength of radiation needed will be
the sum of the energy of the work function
plus the kinetic energy of the ejected elctron.
E
work function
= (4
.
37 eV)
×
(1
.
6022
×
10

19
J
/
eV)
= 7
.
00161
×
10

19
J
E
kinetic
=
1
2
m v
2
=
1
2
(9
.
10939
×
10

31
kg)
×
(9
.
3
×
10
6
m
/
s)
2
= 3
.
93936
×
10

17
J
E
total
=
E
work function
+
E
kinetic
= 7
.
00161
×
10

19
J
+ 3
.
93936
×
10

17
J
= 4
.
00937
×
10

17
J
Since
c
=
ν λ
,
E
=
h ν
=
h c
λ
λ
=
h c
E
=
6
.
626
×
10

34
m
2
·
kg
/
s
4
.
00937
×
10

17
J
×
3
.
0
×
10
8
m
/
s
= 4
.
95788
×
10

9
m
×
10
9
nm
1 m
= 4
.
95788 nm
002
(part 1 of 1) 10 points
Calculate the wavelength of a motorcycle of
mass 275 kg traveling at a speed of 125 km/hr.
1.
1.93
×
10

38
m
2.
2.41
×
10

36
m
3.
1.93
×
10

41
m
4.
6.94
×
10

38
m
correct
5.
2.08
×
10

29
m
Explanation:
v
= 125 km/h = 125000 m/h
m = 275 kg
λ
=
h
m v
=
6
.
626
×
10

34
J
·
s
(275 kg)
125000 m
3600 s
¶
= 6
.
93923
×
10

38
m
003
(part 1 of 3) 10 points
Use the Rydberg formula for atomic hydrogen
to calculate the wavelength for the transition
from
n
= 4 to
n
= 2.
1.
205 nm
2.
8.63 nm
3.
486 nm
correct
4.
2.45 nm
5.
94
.
9 nm
Explanation:
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Cheung, Anthony – Homework 2 – Due: Sep 19 2006, midnight – Inst: McCord
2
c
=
ν λ
, so
ν
=
R
1
n
2
2

1
n
2
1
¶
c
λ
=
R
1
n
2
2

1
n
2
1
¶
c
=
R
1
n
2
2

1
n
2
1
¶
λ
λ
=
c
R
1
n
2
2

1
n
2
1
¶
=
3
×
10
8
m
/
s
(3
.
29
×
10
15
1
/
s)
1
4

1
16
¶
= 4
.
86322
×
10

7
m
= 486
.
322 nm
004
(part 2 of 3) 10 points
What is the name given to the spectroscope
series to which this transition belongs?
1.
Pfund series
2.
Balmer series
correct
3.
Paschen series
4.
Brackett series
5.
Lyman series
Explanation:
005
(part 3 of 3) 10 points
In what region will the light lie?
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 Fall '07
 Fakhreddine/Lyon
 Chemistry, Atomic orbital, midnight – Inst

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