1
Quiz 3 solutions are in order of the questions for version A.
(1). Correct answer B
The wavelength obeys the relation
hc
= φ = 2.54 × 10−19
λ
which lead to result B
(2). Correct answer is A
From the de Broglie relation, p = mv = h/λ; plugging in gives A
(3). Correct answer is B
(∆p)2
1
KE =
'
2m
2m
h
4πδx
2
Plugging in all the numbers gives B
(4). Correct answer is D
The photon energy must be 9(13.6 ev)(1/16 - 1/25). Equating this to
hc
λ
gives the
answer.
(5). Correct answer is D
The maximal energy loss for each scattering takes place with an angle of 180o . For this
h
angle, the change in wavelength is 2 mc
' 4.86pm. If the total change has to 40pm,
this means that 8 collisions is not enough but 9 could be (8 < 40/4.86 < 9
(6). Correct answer is C
The existance of sharp spectral lines was the major motivation behind the Bohr model
(7). Correct answer is A
Light is emitted when at atom transitions from an excited state to a different state,
lower in energy.
(8). Correct answer is C
Electrons can easily be given enough kinetic energy such that their de Broglie wavelength will be well below the wavelength of visible light. This leads to much greater
resolution.
2
(9). Correct answer is A
This atom has a completely filled n=2 level and hence is probably inert.
(10). Correct answer is B
By energy conservation, KE = 6.4 - 13.6/4 =3 ev