Question 1

Placing a secondary mirror in front of the primary mirror

Accepted Answer

The answer of Placing a secondary mirror in front of...

Question 2

Light from each part of the source being observed falls on each part of the primary mirror of a Newtonian telescope not obstructed by the secondary mirror. The important consequence of this is that

Accepted Answer

The light from the entire source is distributed across the primary mirror, so the image does not show a dark spot from the secondary mirror's obstruction.

Question 3

Light from a pointlike light source will enter a person's detector almost parallel if the source is very far away. If one moves closer to the source, the light entering one's detector

Accepted Answer

As one moves closer to a pointlike light source, the light rays entering the detector spread out more, becoming more divergent. This is because the angle subtended by the light source at the detector increases as the distance decreases, causing the light rays to diverge more as they enter the detector.

Question 4

Astronomers sometimes choose the type of reflecting telescope to use as a result of the amount of strain the weight of the mounted equipment will exert on the telescope. Which type of reflector generally results in the MOST strain?

Accepted Answer

The answer of Astronomers sometimes choose the type of reflecting...

Question 5

One advantage of using a Cassegrain telescope is that

Accepted Answer

Cassegrain telescopes allow for observing equipment to be mounted at the back of the telescope, making the setup more balanced and stable compared to a Newtonian telescope where equipment is often mounted at the front.

Question 6

Who developed the first reflecting astronomical telescope?

Accepted Answer

Isaac Newton developed the first successful reflecting telescope in 1668, which is known as the Newtonian telescope.

Question 7

The main reason for building larger optical telescopes on Earth's surface is to

Accepted Answer

Larger optical telescopes collect more light, allowing astronomers to observe fainter objects and gather more data for analysis. This capability is crucial for studying distant galaxies, nebulae, and other celestial phenomena.

Question 8

When light from the concave primary mirror of a telescope is reflected by a small secondary mirror through a hole in the primary to its focus, it is called the

Accepted Answer

The Cassegrain focus involves light being reflected from a telescope's concave primary mirror to a smaller secondary mirror, and then through a hole in the primary mirror to its focus. This configuration is characteristic of Cassegrain telescopes.

Question 9

Some research telescopes have secondary mirrors that block the central part of the larger primary mirror. What problem does this introduce for observations?

Accepted Answer

The secondary mirror blocks a portion of the light that would otherwise be collected by the primary mirror, leading to a reduction in the overall light gathering capability of the telescope. This results in a dimmer image because less light is available to form the image.

Question 10

Which of these optical elements or combinations make up a Newtonian telescope?

Accepted Answer

A Newtonian telescope utilizes a primary concave mirror to gather and focus light, and a secondary flat mirror to reflect the focused light to an eyepiece, making option C correct.

Question 11

Research observatories do NOT use Newtonian reflectors because they

Accepted Answer

Newtonian reflectors are inherently lopsided due to their design, which places the secondary mirror off to the side of the primary optical path. This design can make it challenging to support heavy or complex research instruments, which are often necessary for advanced astronomical work.

Question 12

Compared to the direction of the incoming light, in which way does the light leave the eyepiece of a Newtonian telescope?

Accepted Answer

In a Newtonian telescope, the light collected by the primary mirror is reflected to a flat secondary mirror, which then directs the light at a right angle to an eyepiece located on the side of the telescope. This design allows for efficient observation without looking directly towards the light source.

Question 13

When a ray of light strikes a smooth mirror surface at an angle to the perpendicular, the ray is reflected

Accepted Answer

When a ray of light strikes a smooth mirror surface at an angle to the perpendicular (normal), it is reflected on the other side of the perpendicular but at the same angle as the incoming ray, according to the law of reflection.

Question 14

A particular telescope is set up to use the coudé focus. Which arrangement of mirrors is used to bring the light to this focus?

Accepted Answer

The coudé focus involves a complex arrangement of mirrors, including both plane (flat) and curved mirrors, to direct light to a fixed location outside the telescope's main structure, allowing for stable, heavy, or sensitive instruments to be used without being mounted on the moving telescope itself.

Question 15

A Newtonian telescope uses

Accepted Answer

A Newtonian telescope uses a primary concave parabolic mirror to gather light and a secondary flat mirror at a 45° angle to direct the light to the eyepiece.

Question 16

The prime focus of a reflecting telescope is reached by light after

Accepted Answer

The prime focus of a reflecting telescope is reached by light after one reflection off the primary mirror. Reflecting telescopes use mirrors to gather and focus light, unlike refracting telescopes, which use lenses.

Question 17

The light-gathering power of a telescope depends directly on the

Accepted Answer

The light-gathering power of a telescope is directly related to the area of its primary mirror or lens. A larger primary mirror or lens can collect more light from distant objects, making them appear brighter through the telescope. This is because the amount of light that a telescope can collect is proportional to the square of the diameter of its primary aperture.

Question 18

A Cassegrain reflecting telescope is constructed using a

Accepted Answer

A Cassegrain reflecting telescope uses a concave primary mirror and a smaller convex secondary mirror. The secondary mirror reflects light back through a hole in the primary mirror to the eyepiece or detector.

Question 19

A Newtonian reflecting telescope is constructed using a

Accepted Answer

A Newtonian telescope uses a concave primary mirror to collect and focus light, and a flat, diagonal secondary mirror to reflect the focused light to the eyepiece without the need for a hole in the primary mirror.

Question 20

The major reason astronomers seek funds to build larger telescopes is to

Accepted Answer

Larger telescopes can collect more light from distant objects, allowing astronomers to observe fainter and more distant objects in the universe. This capability is crucial for studying the properties of stars, galaxies, and other celestial bodies.

Quiz 3: Light and Telescopes