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McGill University *
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Course
181
Subject
Astronomy
Date
Apr 3, 2024
Type
Pages
3
Uploaded by DeanInternetRat44
Quiz 3 solution
1
Quiz 3 solution
Mars has nearly zero atmosphere. What colour will the setting Sun look to a viewer on Mars?
white
The Sun emit wave at all wavelength, while the spectrum is peaked at blue-
green. The mixture of colour appears white without the scattering effect of the atmosphere.
When does the Full Moon rise?
At Sunset
Full Moon appears only when the Moon is opposite the Sun. At this position the Moon rise at sunset.
In the Earth's amosphere, how much more scattered is sunlight having wavelength 350 nm compared to light having wavelength 700 nm?
16x
Rayleigh scattering:
Imagine the Earth's obliquity were 0 degrees. Which of the following would be true?
There would be no seasons. I
∝
λ
4
1
=
I
700
nm
I
350
nm
(
)
=
350
700
4
16
Quiz 3 solution
2
The celestial equator and the ecliptic would align. All days would last 12 hours. The Sun would always rise exactly in the East. The constellations of the zodiac would remain the same as they are presently.
Winter in the Southern hemisphere would coincide with Summer in the North
Summer is hot because that's when the Earth is closest to the Sun.
False
Earth is at its closest point to Sun (called Perihelion) in January, which is winter for us. In fact, there is summer because Earthʼs axis is tilted.
On average in the Universe, how much more abundant is calcium compared to gold?
1,000,000 times more
Read from the cosmic elemental abundance diagram, Ca is about 6 orders of magnitude more abundant than Au.
If the Sun magically shut off, how long would it take a viewer on Jupiter to know?
Quiz 3 solution
3
43 minutes
The Earth rotates on its axis once every 24 hours. At what speed is someone standing at the equator moving due to this rotation?
1650 km /hr
In the light bulb demo, when the filament got twice as bright, by approximately how much did its temperature increase?
1.19 times
Stefan Boltzmann Law:
You see Polaris 30 degrees above the horizon. What latitude are you at?
30 degress
In the northern hemisphere, the angle that Polaris is above is horizon is the latitude.
T
=
=
speed of light
778million km
=
3 × 10 m s
8
−1
7.78 × 10
m
11
2590s = 43min
v
=
ωR
=
×
24
2
π
6300 = 1650km/hr
=
L
2
L
1
(
)
T
2
T
1
4
=
T
2
T
1
2
=
4
1
1.19
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