Question 1

Which of the following is the most important feature of a telescope for determining its ability to collect light?

Accepted Answer

The diameter of the primary mirror or lens

Question 2

A telescope has a primary mirror with a diameter of 2 meters. What is the ratio of its light-gathering power compared to a telescope with a 1-meter diameter mirror?

Accepted Answer

4

Question 3

Which type of telescope uses a convex secondary mirror that reflects light back through a hole in the primary mirror, allowing for a compact design and a large range of observations?

Accepted Answer

Cassegrain

Question 4

What is the main advantage of using segmented mirrors in large telescopes like the James Webb Space Telescope (JWST)?

Accepted Answer

They allow the construction of a large mirror using smaller, more manageable pieces.

Question 5

Which equation correctly expresses the relationship between the flux $$F$$ received from a star and its distance $$r$$ from the observer?

Accepted Answer

$$F = \frac{L}{4 \pi r^2$}$$

Question 6

A telescope with a focal length of 2000 mm and an aperture diameter of 200 mm is used to observe two stars. Using the Rayleigh criterion, what is the minimum angular separation $$	heta (in $$arcseconds) that can be resolved? Use $$	heta = \frac{1.22 \lambda}{D}$$, with $$\lambda = 550 nm.$$

Accepted Answer

0.69 arcseconds

Question 7

Which of the following best describes the function of a spectrometer in astronomical observations?

Accepted Answer

It determines the brightness of an object as a function of wavelength, such as color.

Question 8

Why are modern CCDs (Charge-Coupled Devices) preferred over glass plates in astronomical detectors?

Accepted Answer

CCDs have higher quantum efficiency and can detect fainter sources.

Question 9

Which mount type allows a telescope to follow the diurnal motion of the Earth, keeping objects in the sky centered in the field of view?

Accepted Answer

Equatorial mount

Question 10

If a telescope's focal length is decreased while keeping the aperture constant, what happens to the field of view and the image brightness?

Accepted Answer

Field of view increases, image brightness increases

Question 11

Which of the following best explains why astronomers place telescopes in space?

Accepted Answer

To avoid atmospheric turbulence and absorption, allowing for diffraction-limited imaging

Question 12

A telescope's signal-to-noise ratio (SNR) is given by $$SNR = \sqrt{N}$$, where $$N is $$the number of photons detected. If you increase the exposure time by a factor of 4, what happens to the SNR?

Accepted Answer

It doubles

Question 13

Which of the following is a disadvantage of using a larger field of view in a telescope?

Accepted Answer

Lower magnification and lower resolution

Question 14

Which type of reflector telescope uses a diagonal mirror to direct light to the side of the telescope tube?

Accepted Answer

Newtonian

Question 15

What is the main purpose of adaptive optics in ground-based telescopes?

Accepted Answer

To compensate for distortions due to atmospheric turbulence

Question 16

If the quantum efficiency (QE) of a detector is given by $$QE = \frac{N_{net}}{N_{in}}$$, what does a QE of 0.9 mean?

Accepted Answer

90% of incoming photons are detected as electrons

Question 17

Which of the following best describes the inverse square law as it applies to astronomy?

Accepted Answer

The apparent brightness of an object decreases as the square of the distance from the observer increases

Question 18

Which of the following is a real-world application of the plate scale in telescopes?

Accepted Answer

Converting the angular size of an object to its physical size on the detector

Question 19

Which of the following statements about atmospheric windows is correct?

Accepted Answer

They are wavelength ranges where Earth's atmosphere is transparent to incoming radiation

Question 20

A star is observed with two different telescopes: one with a 1-meter aperture and another with a 2-meter aperture. If both observe for the same amount of time, how does the signal-to-noise ratio (SNR) compare between the two telescopes?

Accepted Answer

The 2-meter telescope has twice the SNR of the 1-meter telescope

Telescopes: Principles, Types, and Properties in Physics

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