As light passes from air into a dense but transparent material it
*Refraction of light at a surface between two transparent substances occurs because
the speed of light is different in the two materials.
*A typical refracting telescope is made up of
a long-focal-length lens at the front and a short-focal-length lens at the rear (next to your eye as you look through the telescope).
The main reason for building large optical telescopes on Earth's surface is
to collect more light from faint objects.
*The light-gathering power of a telescope is related directly to the
area of its primary mirror or lens.
What is chromatic aberration in a telescope?
*The light of different colors comes to a focus at different points inside the telescope.
Which of the following is not a defect or problem that occurs in a refracting telescope?
spherical aberration at the primary reflecting surface
Which of the following does not represent a major drawback when developing a refracting telescope for astronomy?
Lenses cannot be made with focal lengths that produce very high magnifications.
*At the mirror of a reflecting telescope, the light reflects from a coated surface rather than refracting through a lens. This eliminates
A light ray strikes a smooth surface of glass at an angle α to the perpendicular. What angle will the reflected ray make with the perpendicular to the surface?
the same angle α on the opposite side of the perpendicular to the incident ray
A Newtonian telescope uses
one curved mirror and one flat mirror at a 45° angle to the curved mirror.
A reflecting telescope used at prime focus does not suffer from chromatic aberration because
regardless of color, all wavelengths of light are reflected by the same amount.
*Spherical aberration can be corrected in a reflecting telescope by
grinding the mirror to a parabolic shape.
*Which of the following characteristics of an astronomical telescope is most important for determining the angular resolution?
the diameter of the objective lens or mirror
*What does the word “seeing” mean to an astronomer using a telescope?
The twinkling and blurring of the image due to air currents in Earth's atmosphere.
It is difficult to improve the angular resolution of optical telescopes located on the surface of Earth beyond a certain limit because
air turbulence distorts the star images more than does the telescope optics.
*To reduce the effects of bad seeing on astronomical images, the best Earth-based sites for modern large astronomical telescopes are
the tops of high mountains.
Approximately what percentage of the light falling on a typical photographic plate from a telescope is actually used to record an image on this plate?
What is a charge-coupled device (CCD)?
an array of electronic sensors which record the charge buildup due to photon absorption
*In spectroscopy, a diffraction grating is a
piece of glass or metal on which many closely spaced grooves have been cut.
*The first nonvisible radiation detected from outer space was
One major difference between radio waves and light is that
radio waves have lower frequencies.
*The first radio energy to be detected from outer space came from the direction of
the Milky Way galaxy, near Sagittarius.
*One way to improve the angular resolution of a radio telescope is to
How does angular resolution for a given diameter of telescope depend on wavelength?