Astronomy-Chapter 3-Lens and Telescopes

The angular resolution of a telescope is limited by the ________ of the telescope and the ________ of the radiation of being observed.

(Diameter) of the telescope and the (Wavelength).

What are the three types of mirrors?

1) Flat or Blair Mirror: They are the same size, same distance mirror but the image is reverse. 2) Concare Mirror or Converging Mirror: They are mirror that zoom on an image. (Example: make-up mirror) 3) Convex Mirror or Diverging Mirror: They are mirror to see wide range of an image. (Example: Car Mirrors or Store Mirror)

What is a CCD (charge-coupled device) Chip?

A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. (Example: Camara)

What is a Interferometer?

An instrument in which the interference of two beams of light is employed to make precise measurements.

________ is the most important quality of an astronomical telescope. A) Magnification B) Resolving Power C) Ability to see at night. D) Rigidity

B) Resolving Power

Telescope X can resolve two stars that are separated by at least 2 second of arc. If telescope Y can resolve two stars that are separated by 1 second of arc, then compared to telescope X: A) Telescope Y has half the resolving power, at most. B) Telescope Y has at lest twice the resolving power. C) Cannot answer without knowing the magnification of each telescope. D)Cannot answer without knowing the diameter of each telescope.

B) Telescope Y has at lest twice the resolving power.

What is refraction?

Bending of light

A large space-based radio-telescope will not suffer from atmospheric scintillation, which causes problems to radio telescopes, and this would be a very significant advantage compared to a land based radio-telescope of the same size. True of False?

False

What is Reflector Telescopes?

Is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. Facts: 1) 99% of modern telescopes are Reflectors. 2) Mirror can be supported from the back. 3) Do not need large, defective, free glasses since surface is coated with reflective material.

What is Refractors Telescopes?

Is a type of optical telescope that uses a lens as its objective to form an image. Facts: 1) Refractors are the first telescopes created. 2) There are many disadvantages in large telescopes: -Large lens are expensive and hard to fabricate. -Large lens will sag in the center since it can only be supported on the edge. -Dispersion causes images to have color fringes (Chromatic Aberration). -Many lens material absorb short wave length light.

What is resolution?

The clarity to see an image. 2) In order to see a better image, the smaller the pixels is the better the resolution. 3) The smaller R is the higher the resolution is. In order to get that wavelength must be small while diameter must be large.

What does a telescope do?

A telescope allows you to see faraway objects. It also gather light, resolve details, and magnify an image.

The main advantage of using radio-telescopes is that: A) Radio-telescopes have high magnification. B) Radio-telescopes are easy to build. C) Radio waves penetrate interstellar dust. D) Radio telescopes have higher resolving power than optical telescopes of similar size. E) Radio telescopes are built of metal and therefore are more rigid.

C) Radio waves penetrate interstellar dust.

The major advantage of space-based telescopes is? A) They have higher magnification. B) They measure the true size of stars. C) They are not affected by atmospheric scintillation. D) They receive image faster.

C) They are not affected by atmospheric scintillation.

What are the two types of lens?

Concave Lens and Convex Lens

What is another name for convex lens?

Converging Lens

Which of the following is an inherent disadvantage of radio telescopes: A) Radio telescopes do not work with visible light. B) Radio telescopes have low magnification. C) Radio signals are very weak, and their photons do not penetrate the atmosphere easily. D) The long wavelength of radio waves results in lower resolving power, compared to other telescopes of the same size. E) All of the above.

D) The long wavelength of radio waves results in lower resolving power, compared to other telescopes of the same size.

What is another name for concave lens?

Diverging Lens

What is Chromatic Aberration?

Lens bend different colors of light through different angles or bend different color at different focus point, just as a prism does.

What is the equation for eyepiece and magnification?

M=fo/fe -Can change the eyepiece for magnification.

A telescope that uses mirror to focus light is called a _________ telescope.

Reflector.

All large modern telescopes are of the ________ type.

Reflector.

All radio telescopes are of the ________ design.

Reflector.

What are the two types of telescopes?

Reflectors and Refractors.

A telescope that uses a lens to focus light is called a _________ telescope.

Refractor.

The light-gathering power of a telescope is determined by the _________ of it's mirror or lens.

Size or Diameter.

What is the Law of Reflection?

The angle of incidence is equal to the angle of reflection.

A 10m diameter telescope has the same light gathering power as the combined light gathering power of 10 telescopes 1 meter in diameter. True or False?

True

The design of radio telescopes is very similar to the design of reflecting telescopes. True or False?

True

How do we solve the problem of Chromatic Aberration?

We need to coat the lens by using two lenses.