Transcript Observational Methods

Observational Methods
Multiple Choice Questions
Test Question
Does this quiz work?
A. Yes
B. No
Observational Methods
1. Which of the following statements about information we receive from space
is FALSE?
A. Electromagnetic radiation travels as a transverse wave.
B. Some forms of information other than electromagnetic radiation are cosmic rays,
neutrinos, gravitational waves, radio waves and spacecraft. Y
C. EM radiation can directly give us information about an objects sky position,
apparent brightness, spectral energy distribution and Doppler shift.
D. X-rays are not a form of EM radiation.
Observational Methods
2. Think about the equation: E = hν. What do the symbols mean?
A. E = energy, h = Planck’s constant, ν = frequency. Y
B. E = energy, h = Boltzmann’s constant, v = velocity.
C. E = energy, h = Planck’s constant, v = velocity.
D. E = energy, h = Boltzmann’s constant, v = frequency.
Observational Methods
3. Which of the following is the correct form of Pogson’s equation?
A. m1 – m2 = 2.5log10(F2/F1).
B. m2 – m1 = -2.5log10(F2/F1). y
C. m2 – m1 = -2.5log10(F1/F2).
D. m1 – m2 = 2.5log10(F1/F2).
Observational Methods
4. There are two main observing windows from Earths surface, what are
these?
A. Radio and optical. Y
B. Optical and infrared.
C. X-rays and optical.
D. Ultraviolet and optical.
Observational Methods
5. The equation for Flux is F = L/4πd2. What are the units of flux?
A. W s-1 m-2.
B. J s-1 m-1.
C. J s-1 m-2. y
D. W m-2.
Observational Methods
6. What is Snell’s law?
A. n1 = n2sinθ1 / sinθ2.
B. n1sinθ2 = n2sinθ1.
C. n1 = n2sinθ2 / sinθ1. y
D. n2 = (sinθ2 / sinθ1) x n1.
Observational Methods
7. Which of the following is a correct form of an equation for the height of an
image at the focal plane?
A. h = Fptanαo. y
B. h = Fptanαp.
C. h = Fetanαo.
D. h = Fetanαp.
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8. Which of the following models of reflective telescopes have a hole in the
primary mirror?
A. Nasmyth Focus.
B. Coudé Focus.
C. Newtonian.
D. Cassegrain. y
Observational Methods
9. The speed (or focal ratio) is given by…
A. F = f / D.
B. f = F / D. y
C. F = D / f.
D. f = D / F.
Observational Methods
10. The Rayleigh criterion is given by…
A. θmax = 1.22sinλ / D. With θ in radians.
B. θmax = 1.22sinλ / D. With θ in degrees.
C. θmax = 1.22λ / D. With θ in degrees.
D. θmax = 1.22λ / D. With θ in radians. y
Observational Methods
11. Which of the following lists of the advantages of reflecting telescopes over
refracting telescopes is FALSE?
A. Reflectors don’t suffer from astigmatism, coma and spherical aberration. Y
B. Glass can be chosen for its thermal properties rather than its optical properties.
C. There is no chromatic aberration.
D. Can use distributed mechanical support for mirror to account for sagging.
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12. Schmitt-Cassegrain telescopes require a large corrector plate, true or
false?
A. True. y
B. False.
Observational Methods
13. Which of the following statements about equatorial mounts is FALSE?
A. Compensation for Earths rotation only requires uniform motion in one axis.
B. They require a lot of space.
C. They are cheap to engineer. y
D. They flex.
Observational Methods
14. Which of the following statements about Alt-Az mounts is FALSE?
A. They are not used very often in large telescopes any more. y
B. They require tracking in 2 axes to compensate for the Earth’s rotation.
C. They are simple to engineer.
D. None of the above are false.
Observational Methods
15. If an average of 1500 photons arrive at a detector but only an average of
7.5 photons are detected, what is the quantum efficiency of the detector?
A. 0.75.
B. 5.
C. 200.
D. 5 x 10-3. y
Observational Methods
16. What is the signal to noise ratio given by?
A. SNR = strength of signal / strength of noise. Y
B. SNR = strength of noise / strength of signal.
C. SNR = (strength of noise – background) / strength of signal.
D. SNR = (strength of signal – background) / strength of noise.
Observational Methods
17. Which of the following disadvantages of photographic plates is incorrect?
A. They have a low quantum efficiency.
B. There is a delay between taking observation and getting the data.
C. They have a lower pixel density than CCDs i.e. they are more grainy. y
D. They require a very well controlled development of plate/film for consistency and
repeatability.
Observational Methods
18.Which of the following have a linear response to photons?
A. CCDs only.
B. CCDs and Photomultipliers only. y
C. CCDs and photographic plates only.
D. Photomultipliers only.
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19. The spectral resolving power for a spectrometer is given by…
A. R = Nm.
B. R = Δλ / λ.
C. R = c / vΔλ. Y
D. R = Nm / λ
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20. The groves on a diffraction grating are of what scale?
A. The millimetre scale.
B. The micrometre scale. y
C. The nanometre scale.
D. They vary form grating to grating so that it is not possible to say if they are
normally of any the sizes above.
Observational Methods
21. What is the angular dispersion?
A. It describes how much the spectrum is spread in angle after passing through a
lens or grating. y
B. It describes how the spectrum will be spread along the detector.
C. It describes the angle of the light before it passes through a lens or grating.
D. None of the above.
Observational Methods
22. For a reflection grating, if you know the order of maximum ‘m’, the
wavelength ‘λ’, the separation of the groves in the grating ‘d’, is it possible
to calculate the angle of diffraction?
A. No, you need to know one more variable. Y
B. No, you need to know two more variables.
C. Yes but one of the variables above is not needed.
D. Yes you can using all of the above variables.
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23. A Jansky is a unit of radio power, what are its units?
A. W m-1 Hz-1.
B. W m-2 Hz-2.
C. W m-2 Hz-1. y
D. W m-2.
Observational Methods
24. An optical telescope with a primary diameter of 1m viewing light of 400nm
has an angular resolution of 4 x 10-7, what diameter would a radio
telescope dish need to be to achieve the same angular resolution if it
received radiation of 1cm?
A. 25m.
B. 250m.
C. 2500m.
D. 25000m. y
Observational Methods
25. Grazing incidence optics can be used to view what sort of radiation?
A. EM radiation of wavelength ≤ 400 nm.
B. Cosmic rays.
C. Neutrinos.
D. EM radiation of wavelength ≤ 100 nm. y