Download UNIT TWO Astronomical Instruments and Light

UNIT TWO
Astronomical Instruments and Light
True/False
Indicate whether the sentence or statement is true or false.
____
1. 300 nm light has a lower frequency than 500 nm light.
____
2. Light can behave as a particle or as a wave.
____
3. The amount of energy a photon carries depends on its wavelength.
____
4. Reflecting telescopes are no longer popular with astronomers because they are expensive and suffer
from chromatic aberration.
____
5. One of the advantages of charge-coupled devices over photographic plates is that a CCD can record
bright and faint objects on the same exposure.
____
6. The nucleus of the hydrogen atom consists of a single neutron.
____
7. An absorption spectrum is also called a bright line spectrum.
____
8. An atom that has lost an electron is called an ion.
____
9. The Lyman series lines of hydrogen all lie in the infrared.
____ 10. Hydrogen lines are weak in the spectra of hot stars because many of the hydrogen atoms have their
electrons in levels above the second level.
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
____ 11. What is the wavelength of the longest wavelength light that can be seen with the human eye?
a. 400 nm
b. 4000 nm
c. 7000 nm
d. 700 nm
e. 3 x 108 m
____ 12. What is the wavelength of the shortest wavelength light that can be seen with the human eye?
a. 400 nm
b. 4000 nm
c. 7000 nm
d. 700 nm
e. 3 x 108 m
____ 13. ____________ has (have) wavelengths that are longer than visible light.
a. Gamma-rays
b. Ultraviolet light
c. Infrared radiation
d. X-rays
e. a, b and d above
____ 14. ____________ has (have) wavelengths that are shorter than visible light.
a. Gamma-rays
____ 15.
____ 16.
____ 17.
____ 18.
____ 19.
____ 20.
____ 21.
b. Ultraviolet light
c. Infrared radiation
d. Radio
e. a and b
Astronomer's build telescopes on tops of mountains because
a. there is less air to dim the light.
b. the seeing is better.
c. CCDs work better when there is less oxygen in the air.
d. all of the above
e. a and b
A _________ has a few million light sensitive diodes in an array about a half inch square.
a. photometer
b. charge-coupled device
c. spectrograph
d. photographic plate
e. grating
A new generation of telescopes is currently being built that overcomes the limitations of the older large
telescopes. Some of these new telescopes
a. use segmented mirrors.
b. use mirrors that are very thin.
c. use active optics to control the shape of the mirror.
d. all of the above.
e. none of the above
What is the magnification of a telescope and eyepiece if the telescope objective has a focal length of
200 cm and the eyepiece has a focal length of 0.2 cm
a. 400 times
b. 4000 times
c. 100 times
d. 1000 times
e. 40 times
The resolving power of a telescope with a diameter of 232 cm is
a. 0.05 arc seconds.
b. 232 arc seconds.
c. 2.32 arc seconds.
d. 5 arc seconds.
e. 11.6 arc seconds.
A telescope that suffers from chromatic aberration and has a low light gathering power is most likely
a. a small diameter reflecting telescope.
b. a small diameter refracting telescope.
c. a large diameter refracting telescope.
d. a large diameter reflecting telescope.
e. the Hubble Space Telescope.
Which of the following types of radiation require the use of space based telescopes in order to collect
astronomical data?
I.
II.
III.
IV.
Gamma-Ray
Infrared
Radio
Ultraviolet
V.
____ 22.
____ 23.
____ 24.
____ 25.
____ 26.
X-Ray
a. II and III
b. I and V
c. II, III, IV
d. I, IV, and V
e. All of them
A wave traveling at a speed of 90 meters per second with a frequency of 60 Hz would have a
wavelength of
a. 5400 meters.
b. 540 nm.
c. 1.5 meters.
d. 60 meters.
e. 90 meters.
A beam of light from a laser has a wavelength of 600 nm, what is the frequency of this light?
a. 5 x 1014 Hz
b. 6000 Hz
c. 3 x 108 m/s
d. 2 x 10-15 Hz
e. 1.8 x 1012 Hz
What is the energy of the photon whose wavelength is 400 nm?
a. 1.2 x 1012 m
b. 1.3 x 10-5 m
c. 2.7 x 10-30 Joules
d. 5.0 x 10-19 Joules
e. 7.5 x 104 Hertz
Absolute zero is
a. zero degrees Celsius.
b. the temperature at which atoms have no remaining energy from which we can
extract heat.
c. the temperature at which water freezes.
d. both a and c
e. none of the above
A plot of the continuous spectra of five different stars are shown in the figure below. Based on these
spectra, which of the stars is the hottest?
a. Star A
b. Star B
c. Star C
d. Star D
e. Star E
____ 27. An atom that is excited
a. is also ionized.
b. is an isotope.
c. has had its electron moved to the lowest energy level.
d. can emit a photon when the electron moves to a lower energy level.
e. can emit a photon when the electron moves to a higher energy level.
____ 28. The table below lists the color index for each of several stars. Which star in this table would have the
lowest temperature?
Star Name
Boo
Peg
Leo
Leo
Peg
Color Index
+1.23
-0.23
+0.08
-0.11
+1.57
a.
Boo
b.
Peg
c.
Leo
d.
Leo
e.
Peg
____ 29. In the diagram below, which of the transitions would absorb a photon with the smallest energy.
a. Transition 1
b. Transition 2
c. Transition 3
d. Transition 4
e. Transition 5
____ 30. You are standing near a railroad track and a train is moving toward you at 60 mph and blowing its horn.
What will you notice as the train moves past you?
a. As the train approaches, the horn will sound lower in pitch than when it is moving
away.
b. As the train approaches, the horn will sound higher in pitch than when it is moving
away.
c. There will be no change in the pitch of the horn as it moves by.
d. The horn will get louder as the train moves away from me.
e. The horn will get quieter as the train moves toward me
____ 31. Which of the following can be determined by using the Doppler effect?
I.
II.
III.
IV.
The speed at which a star is moving away from an observer.
The transverse velocity of a star.
The radial velocity of a star.
The speed at which a car is traveling toward an observer.
a. I & IV
b. II & III
c. II & IV
d. I & III
e. I, III, & IV
____ 32. The diagram below illustrates a light source, a gas cloud, and three different lines of sight. Along which
line of sight would an observer see an emission spectrum?
a. 1
b. 2
c. 3
d. 2 and 3
e. none of them
____ 33. The table below lists the spectral types for each of five stars. Which star in this table would have the
highest temperature?
Star Name
For
Cet
35 Ari
Tri
Per
Spectral Type
F8
M7
B3
A0
O7
a.
For
b.
Cet
c. 35 Ari
d.
Tri
e.
Per
____ 34. The table below lists the spectral types for each of five stars. Which star in this table would have the
have the strongest hydrogen lines?
Star Name
Spectral Type
For
Cet
35 Ari
Tri
Per
____ 35.
____ 36.
____ 37.
____ 38.
____ 39.
F8
M7
B3
A0
O7
a.
For
b.
Cet
c. 35 Ari
d.
Tri
e.
Per
The radiation emitted from a star has a maximum intensity at a wavelength of 300 nm. What is the
temperature of this star?
a. 300 K
b. 100 K
c. 900,000,000 K
d. 90,000 K
e. 10,000 K
The radiation emitted from a star has a maximum intensity at a wavelength of 500 nm. What is the
temperature of this star?
a. 6,000 K
b. 5,000 K
c. 1.5 x 109 K
d. 500 K
e. 10,000 K
At what wavelength would a star radiate the greatest amount of energy if the star has a surface
temperature of 10,000 K?
a. 10 nm
b. 100 nm
c. 300 nm
d. 1.0 x 104 nm
e. 3.0 1010 nm
One star has a temperature of 10,000 K and another star has a temperature of 5000 K Compared to
the cooler star, how much more energy per second will the hotter star radiate from each square meter
of its surface?
a. 16 times
b. 2 times
c. 1 x 1016 times
d. 625 times
e. 6.3 x 1014 times
The H line has a wavelength of 434.0 nm when observed in the laboratory. If the H line appears in a
stars spectrum at 434.5 nm, what is the radial velocity of the star?
a. 346 km/sec away from the observer.
b. 346 km/sec toward the observer.
c. 1.3 x 108 m/sec away from the observer.
d. 1.3 x 108 m/sec toward the observer.
e. The radial velocity of the star can not be determined from this information.
____ 40. The binding energy of the first level in an atom is 2.2 x 10-18 J, and the binding energy of the second
energy level is 1.6 x 10-18 J. What is the energy of the photon that is emitted if an electron moves from
the second level to the first?
a. 3.3 x 10-18 J
b. 3.5 x 10-36 J
c. 1.4 J
d. 3.5 x 10-18 J
e. 6.0 x 10-19 J
Completion
Complete each sentence or statement.
41. A(n) ____________ telescope has an objective that is a lens.
42. A refracting telescope suffers from ___________ aberration.
43. A ____________ is used to measure the brightness and color of stars.
44. A wave on a lake is found to have a wavelength of 2 m and a frequency of 0.3 Hz. What is the speed of
this wave?
45. A telescope that is 1.0 meters in diameter has a focal length of 10 meters. If an eyepiece with a focal
length of 0.01 meters is used with this telescope, what is the magnification of the telescope and
eyepiece?
46. In the diagram below, draw the transition that would emit a photon with the smallest wavelength.
47. The _____________ of a star can be determined from its color.
48. The process of removing an electron from a stable nucleus is known as ____________.
49. ___________ is a measure of the amount of energy due to the motion of the particles in a gas. liquid,
or solid.
50. If one star has a temperature of 4000 K and another star has a temperature of 40,000 K, how much
more energy per second will the hotter star radiate from each square meter of its surface?
____________
Essay
51. Why might astronomers someday establish an observatory on the moon? Why would radio
astronomers prefer the far side of the moon for their observatory?
52. Why can infrared telescopes operate from high flying aircraft and high mountain tops whereas X-ray
telescopes must be placed in orbit?
53. Why are the Balmer lines weak in the spectra of hot and cool stars, but strong in the spectra of
intermediate temperature stars?
unit2_test
Answer Section
TRUE/FALSE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
F
T
T
F
T
F
F
T
F
T
MULTIPLE CHOICE
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
D
A
C
E
E
B
D
C
A
B
D
C
A
D
B
A
D
E
E
B
E
B
E
D
E
A
C
A
39. A
40. E
COMPLETION
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
refracting
spherical
photometer
0.6 m/s
1000 x
a line from the Fifth Level to the First level
temperature
ionization
Heat
10,000 times
ESSAY
51. Answer not provided.
52. Answer not provided.
53. Answer not provided.