Question 1

Refraction is the:
A) bending of light as it enters a dense but transparent material at an angle perpendicular to the surface of the material.
B) bending of light around the sharp edge of an obstacle.
C) change in direction of light when it bounces off a smooth surface.
D) change in the color of light when it enters a transparent but colored material, such as glass.

Accepted Answer

Refraction is the bending of light as it enters a dense but transparent material at an angle perpendicular to the surface of the material.

Question 2

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:
A) Cassegrain focus.
B) Newtonian focus.
C) coudé focus.
D) prime focus.

Accepted Answer

The Cassegrain focus is the correct description for the setup described in the question, where light is reflected by a secondary mirror through a hole in the primary mirror to the focus. The Newtonian focus is also a type of reflecting telescope design, but it uses a flat secondary mirror rather than a convex one. The coudé focus is a specific type of Cassegrain focus used for high-resolution spectroscopy. The prime focus is a different setup where the primary mirror is used as the entrance pupil, without a secondary mirror.

Question 3

What is refraction of light?
A) the breaking of white light into its composite colors
B) the change in direction of a light ray when it reflects on a material that is denser than the one in which it is traveling
C) the absorption of light as it traverses a dense, transparent material
D) the change in direction of a light ray as it passes at an angle from one transparent material to another that has a different optical density

Accepted Answer

Refraction of light is the change in direction of a light ray as it passes at an angle from one transparent material to another that has a different optical density. This is commonly observed when a straw in a glass of water appears bent due to the refraction of light passing from the air to the water.

Question 4

A Newtonian reflecting telescope is constructed using a:
A) concave primary mirror and a flat, diagonal secondary mirror.
B) concave primary mirror and a concave secondary mirror that reflects light through a hole in the primary mirror.
C) concave primary mirror and a convex secondary mirror that reflects light through a hole in the primary mirror.
D) convex primary mirror and a flat, diagonal mirror mounted at 45° to the primary mirror.

Accepted Answer

A Newtonian reflecting telescope uses a concave primary mirror to gather and focus light, and a flat, diagonal secondary mirror to reflect the light to the eyepiece. This configuration produces a high-quality image and is the most common design for reflecting telescopes. B and C describe a Cassegrain reflecting telescope, and D describes a type of reflecting telescope known as a Schmitt-Cassegrain.

Question 5

A Cassegrain reflecting telescope is constructed using a:
A) concave primary mirror followed by a smaller convex secondary mirror that reflects light back through a hole in the primary mirror.
B) curved primary mirror followed by a series of both plane and curved mirrors that channel the light to a remote location that is fixed with respect to Earth.
C) concave primary mirror and concave secondary mirror that reflects light back through a hole in the primary mirror.
D) concave primary mirror and a flat, diagonal secondary mirror mounted at a 45° angle to the telescope axis.

Accepted Answer

A Cassegrain reflecting telescope uses a concave primary mirror and a smaller convex secondary mirror to reflect light back through a hole in the primary mirror.

Question 6

If you create a spectrum with a prism as Newton did and then probe the temperature with thermometers that you have kept in the dark,you will find that the thermometer will show a temperature rise when placed:
A) in the visible part of the spectrum but nowhere else.
B) in the visible part of the spectrum and in the invisible region just beyond the red but nowhere else.
C) in the visible part of the spectrum and in the invisible region just beyond the violet but nowhere else.
D) anywhere from the invisible region beyond the red, through the visible, through the invisible region beyond the violet.

Accepted Answer

The thermometer will show a temperature rise anywhere from the invisible region beyond the red, through the visible, through the invisible region beyond the violet. This is because the thermometer is measuring the amount of energy being emitted in the form of heat, and all colors on the spectrum emit energy in different amounts. While the visible part of the spectrum emits the most energy, there is still some energy being emitted in the invisible regions beyond the red and violet. Therefore, the thermometer will show a temperature rise in all these regions.

Question 7

A Newtonian telescope uses:
A) only one mirror with its front surface shaped into a parabola.
B) one curved mirror and one flat mirror at a 45° angle to the first mirror axis.
C) two flat mirrors inclined to each other at a right angle.
D) two curved mirrors, one convex, the second concave in shape.

Accepted Answer

A Newtonian telescope uses one curved mirror (parabolic) to reflect and concentrate light, and a flat mirror at a 45° angle to reflect the light out of the side of the telescope and into an eyepiece. This design is simple and compact, and provides a large, unobstructed view of the sky. Option A describes a single-mirror design, which is not a Newtonian telescope. Option C describes a design of two flat mirrors, which do not concentrate the light effectively. Option D describes a combination of mirrors that would not form a typical Newtonian telescope.

Question 8

One advantage of using a Cassegrain telescope is that:
A) larger mirrors can be used with a Cassegrain telescope than with a Newtonian telescope of similar size.
B) Cassegrain telescopes use spherical mirrors, which are easier to manufacture than the parabolic mirrors required by other telescopes.
C) Cassegrain telescopes have holes cut out of their primary mirrors to make them lighter.
D) observing equipment mounted on a Cassegrain telescope is more balanced and stable than if it were mounted on a Newtonian telescope.

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 9

The prime focus of a reflecting telescope is reached by light after:
A) one reflection.
B) refraction through one lens and reflection at one mirror.
C) reflection at two mirrors.
D) refraction at one lens.

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 10

A particular telescope is set up to use the coudé focus.Which arrangement of mirrors is used to bring the light to this focus?
A) a curved primary mirror followed by a series of plane and curved mirrors that channel the light to a remote and fixed location
B) a concave primary mirror followed by a convex secondary mirror that reflects light through a hole in the primary mirror
C) a concave primary mirror followed by a concave secondary mirror that reflects light through a hole in the primary mirror
D) a concave primary mirror and a flat, diagonal secondary mirror mounted at a 45° angle to the telescope axis

Accepted Answer

The coudé focus uses a curved primary mirror followed by a series of plane and curved mirrors to direct the light to a fixed location, often outside the telescope structure.

Question 11

Research observatories do NOT use Newtonian reflectors because they:
A) cannot be made large enough for modern astronomical work.
B) are inherently lopsided and cannot support heavy research instruments.
C) are more sensitive to atmospheric distortions than are refractors.
D) require two mirrors, whereas the Cassegrain requires only one.

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

The BEST shape for the cross-section of a simple astronomical mirror to have in order to produce the sharpest images of very distant objects at its prime focus is:
A) parabolic.
B) elliptical.
C) perfectly flat and smooth.
D) spherical.

Accepted Answer

A parabolic mirror is the ideal shape for producing sharp images at the prime focus. This is because it can focus all the light that comes in from a distant object to a single point, allowing for minimal distortion and the clearest possible image. Spherical mirrors, on the other hand, suffer from spherical aberration, which results in out-of-focus and distorted images. Elliptical mirrors can produce sharper images than spherical mirrors, but they still suffer from some distortion. A flat mirror would be unable to focus light at all, since it would reflect light away in all directions rather than concentrating it at a single point. Therefore, A) parabolic is the best choice for producing sharp images at the prime focus of an astronomical mirror.

Question 13

The MAIN reason for building large optical telescopes on Earth's surface is to:
A) bring astronomical objects closer for more detailed examination by scientists.
B) collect more light from faint objects.
C) enhance national prestige, with no scientific reason.
D) nullify the effects of Earth's atmosphere and thus produce higher-resolution photographs.

Accepted Answer

Large optical telescopes on Earth's surface are built to collect more light from faint objects, allowing astronomers to observe and study them in more detail. This is important as many astronomical objects emit very little light and are difficult to observe without the use of large telescopes. While reducing the effects of Earth's atmosphere is also a consideration, the primary reason for building large telescopes is to increase their light-collecting power. National prestige is not a scientific reason for building telescopes.

Question 14

Which of the following optical elements or combinations make up a Newtonian telescope?
A) two curved mirrors, one concave, the second convex
B) two lenses, to produce an image the correct way around
C) one concave and one flat mirror
D) one concave focusing mirror

Accepted Answer

A Newtonian telescope uses a concave primary mirror to gather light and a flat secondary mirror to reflect the image to the eyepiece.

Question 15

Who was the first astronomer to build and use a telescope to observe the night sky?
A) Galileo
B) Copernicus
C) Tycho Brahe
D) Newton

Accepted Answer

Galileo was the first astronomer to build and use a telescope to observe the night sky. He made many important discoveries using his telescope, such as the moons of Jupiter, the phases of Venus, and the mountains and craters on the moon. While Copernicus proposed the heliocentric model of the solar system and Tycho Brahe made many observational measurements, Galileo's use of the telescope revolutionized astronomy and our understanding of the cosmos.

Question 16

Compared with the direction of the incoming light,in which way does the light leave the eyepiece of a Newtonian telescope?
A) at a variable angle depending on the direction of the source in the sky
B) in the same direction
C) in the reverse direction, back toward the source
D) at right angles

Accepted Answer

In a Newtonian telescope, the light is reflected by a secondary mirror at a right angle to the incoming light, directing it out the side of the telescope through the eyepiece.

Question 17

When a ray of light strikes a smooth mirror surface at an angle to the perpendicular,the ray is reflected:
A) on the "other" side of the perpendicular but at the same angle as the incoming ray.
B) in reverse along its original (incoming) path.
C) at various angles, depending on wavelength.
D) so that it travels along the perpendicular to the surface of the mirror.

Accepted Answer

According to the law of reflection, when a ray of light strikes a smooth mirror surface at an angle to the perpendicular, it is reflected on the "other" side of the perpendicular but at the same angle as the incoming ray. This means that the angle of incidence is equal to the angle of reflection. Therefore, option A is the best choice.

Question 18

The MAIN reason astronomers seek funds to build larger telescopes is to:
A) measure a wider spectrum of light from stars.
B) collect more light from distant objects.
C) provide magnified images of stars.
D) bring stars closer to Earth.

Accepted Answer

The main reason astronomers seek funds to build larger telescopes is to collect more light from distant objects. This allows them to study fainter and more distant objects in greater detail, including observing and measuring their properties such as composition, temperature, and movement.

Question 19

Astronomers sometimes choose the type of reflecting telescope they use based on the amount of strain the weight of their mounted equipment will exert on the telescope.Which type of reflector generally results in the MOST strain?
A) Cassegrain focus
B) Newtonian focus
C) prime focus
D) coudé focus

Accepted Answer

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

Question 20

Who developed the first reflecting astronomical telescope?
A) Ptolemy
B) Isaac Newton
C) Galileo
D) Copernicus

Accepted Answer

Isaac Newton developed the first reflecting astronomical telescope in 1668.

Quiz 3: Light and Telescopes

Refraction is the:

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:

What is refraction of light?

A Newtonian reflecting telescope is constructed using a:

A Cassegrain reflecting telescope is constructed using a:

If you create a spectrum with a prism as Newton did and then probe the temperature with thermometers that you have kept in the dark,you will find that the thermometer will show a temperature rise when placed:

A Newtonian telescope uses:

One advantage of using a Cassegrain telescope is that:

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

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

Research observatories do NOT use Newtonian reflectors because they:

The BEST shape for the cross-section of a simple astronomical mirror to have in order to produce the sharpest images of very distant objects at its prime focus is:

The MAIN reason for building large optical telescopes on Earth's surface is to:

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

Who was the first astronomer to build and use a telescope to observe the night sky?

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

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

The MAIN reason astronomers seek funds to build larger telescopes is to:

Astronomers sometimes choose the type of reflecting telescope they use based on the amount of strain the weight of their mounted equipment will exert on the telescope.Which type of reflector generally results in the MOST strain?

Who developed the first reflecting astronomical telescope?