Multiple Choice Questions
a)
Skip
- The solar spectrum has its maximum
intensity in terms of watts per square centimeter at a wavelength
corresponding to _____
a)
the
maximum of the ozone absorption spectrum
b)
the
ultraviolet region
c)
the
visible region
d)
a
wavelength of about 10−7 meters
- The spectrum of solar radiation above
the earth's atmosphere has its maximum intensity in the _____
a)
ultraviolet
region
b)
region
of 100×1006 meters
c)
visible
region
d)
infrared
region
- Representative wavelengths for
ultraviolet and infrared radiation, respectively, are ___
a)
0.1
and 1 microns
b)
1 and
10 microns
c)
10 and
100 microns
d)
100
and 1000 microns
- You can easily feel the heat from the
sun through a glass window, but behind a sheet of glass you do not feel
the heat radiated from a fire in a fireplace. This is because _____
a)
glass
is transparent to visible light and opaque to infrared
b)
the
fireplace emits essentially pure ultraviolet radiation
c)
glass
is opaque to visible light and transparent to infrared
d)
the
sunlight is extremely infrared
- BONUS Of the solar radiation
incident on the earth's upper atmosphere, about _____, on average, is available
at ground level.
a)
1/8
b)
1/4
c)
1/2
d)
100%
- Your house foundation and basement
floor are made up of 1000 ft3 of concrete. About
how many Btu are required to raise the temperature of this mass from 0°C
to 40°C? Given: 22 Btu/ft3⋅°F for concrete.
a)
1,600,000
b)
900,000
c)
22,000
d)
40,000
e)
1,800
f)
40
- BONUS A flat-plate solar
collector has a useful upper temperature limit of about _____°C.
a)
2
b)
10
c)
20
d)
100
e)
200
f)
1000
- Skip
- In Boulder (latitude 40° N), a
flat-plate collector should be tipped at an angle from the horizontal of
about _____ in order to maximize the annual direct plus diffuse sunlight
that it collects.
a)
zero
degrees (flat on the ground)
b)
90
degrees (upright)
c)
55 degrees
d)
15
degrees
- At 40° N latitude a south-facing
vertical surface, such as a window, has incident on it on a clear winter
day roughly _____
a)
157 Btu/m2
b)
200 Btu/cm2
c)
20 cal/min⋅cm2
d)
20 Btu/m2
e)
1600 Btu/in2
f)
1600 Btu/ft2
g)
1600 Btu/m2
h)
1600 Btu/cm2
- skip
- A parabolic reflector _____
a)
can be
used for solar collection systems only if the overall efficiency is less than
5%
b)
focuses
both the direct and diffuse components of sunlight
c)
focuses
only the diffuse component of sunlight
d)
focuses
only the direct component of sunlight
- Good photovoltaic cells have an
efficiency of approximately _____
a)
28 to
38%
b)
14 to
17%
c)
2 to
6%
d)
38 to
58%
- BONUS It has not been practical to
enhance the performance of silicon photovoltaic cells by using lenses with
high concentration ratios because _____
a)
the
extreme magnification makes the sun's image too large to match the surface of
the solar cell
b)
the
Carnot efficiency cannot exceed the maximum
c)
the
solar cell efficiency is reduced at the resulting high temperatures
d)
the
lenses are more expensive per square centimeter than are the silicon solar
cells
- Only about _____ of the power in the
solar spectrum is in a wavelength region to which silicon photovoltaic
cells are sensitive.
a)
47%
b)
57%
c)
67%
d)
77%
e)
none
of the above
- The reason that photovoltaic cells are
not generally competitive with fossil fuel–fired power plants is _____
a)
the
cost of raw silicon is too high
b)
the expense
of growing crystals and fabricating the cells is too high
c)
the
efficiency is only 2%
d)
they
cover too much land area
