## Astronomy unit test 4

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SaintSchon  on June 4, 2012

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# Astronomy unit test 4

 The Newtonian focus telescope is an example of a __ telescope.Reflecting.
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#### Definitions

The Newtonian focus telescope is an example of a __ telescope. Reflecting.
In a reflecting telescope the objective is a ____. Mirror.
In a refracting telescope the objective is a ____. Lens.
The Cassegrain telescope is an example of a ____ telescope. Reflecting.
The purpose(s) of the objective in a telescope is to _____. form a real image.
collect light over an area larger than our eye's pupil.
The distance from the objective of a telescope to the place where the image of a distant object is focused, is called the _____ of the objective. Focal length.
The distance between the image that a distant object forms and a lens or mirror is the _____ of the lens or mirror. Focal length.
Light from a distant source passing through a simple convex lens is brought to an image at a distance L from the lens. L is termed the ___. Focal length.
The real image of an astronomical object seen in a telescope is formed by the ____. objective.
The term aperture is shorthand for the _____. area of the objective.
Single-dish radio telescopes are usually designed to be very large in size. This is because All of the above.
Single-dish radio telescopes are usually concave metal dishes. This means that they are reflecting telescopes.
Radio telescopes are _______ telescopes reflecting
The index of refraction of a certain type of glass is 1.5. Given that speed of light in vacuum is 300,000 km/s, what is the speed of light in the glass? 200,000 km/s.
When a light ray travels from air to glass which way does its direction change? it bends toward the normal to the glass surface.
When a light ray travels from water to air, which way does its direction change? it bends away from the normal to the water surface.
For a material, the ratio of the speed of light in a vacuum to that of the speed of light in the material, is the material's ______. Index of refraction.
The index of refraction for a substance is defined as ______. Ratio of speed of light in a vacuum to that of speed of light in the material.
In optics, angles are measured from ____ to the direction of the light travel. The normal.
The index of refraction of water is greater than air. When light passes from air to water at an angle, the light is _____. Bent toward from the normal.
When the angle of incidence increases, the angle of reflection ____. Increases by the same amount.
Suppose a light ray is incident on a surface and that part of the ray is reflected and part refracted as shown in the figure. Suppose the index of refraction of the second material is greater than that of the first. What is the prediction of the law of reflection for the reflected ray? Angle of incidence equals angle of reflection.
The magnifying power of a telescope is _______. The ratio of the angular size of an object when viewed with the telescope to the angular size without the telescope.
Which has the larger light gathering power? A telescope of 9 cm diameter and focal length of 150 cm..
The light-gathering power of a telescope increases as the aperture of the telescope is enlarged. Correct.
The resolving power of a telescope is _____. a measure of the minimum separation of two stars that can be detected with the telescope..
The minimum angular separation of two stars that can be seen be a particular telescope is called the ____ power of that telescope. Resolving.
The main purpose(s) of the objective of a telescope is(are) to _____. Collect light from a large area.
Produce a real image.
The main purpose(s) of the secondary in a telescope is(are) to _____. redirect the light beam to a convenient location.
The main purpose(s) of the correcting lens on a compound telescope is(are) to _____. improve the image.
The primary purpose of the ____ is to magnify, for easy inspection, the image which the objective forms. Eyepiece
The speed of light in a vacuum is ____. 3 x 10^8 m/s
Suppose you have a telescope with a resolution of 3 sec of arc. Could you resolve two stars if
Case 1 stars are 1 sec of arc apart
Case 2 stars are 4 sec of arc apart?
No for 1, yes for 2.
If the constant in Wien's law is about 0.003 and the most energy of a star's emission is observed to be emitted at 4 x 10-7 m, then the star's temperature is __ degrees Kelvin. 7,500.
The lowest temperature which can be reached in principle by mechanical means is approximately ____ . -273 degrees Celsius.
(consider the following photograph of an overexposed star image). The cross is caused by _____. diffraction off the secondary mirror's supporting structure.
The ideal image of a star in a telescope is a small disk surrounded by faint rings. The disk is called the _____ disk. Airy
If the constant in Wien's law is about 0.003 and the temperature of a star is 3000 K (a cool red star) then the wavelength at which the most energy is emitted is _____ m. (note units) 10^6.
The Sun produces most of its energy by a nuclear reaction called the proton-proton cycle. correct

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