Physics 9.1.1-2 Astronomical Telescopes and Reflecting Telescopes

18 flashcards · Physics · by TheoTyson

1. What is the function of a concave lens?

   Spreads an incident beam of light into a diverging emergent beam.

2. What is the function of a convex lens?

   Focuses light rays as they enter the lens.

3. What is the principal axis?

   The perpendicular line that passes through the centre of the lens.

4. What is the principal focus?

   The point where the light rays that are parallel to the principal axis converge.

5. What is the focal length?

   The distance between the principal focus and the centre of the lens.

6. What is a refracting telescope?

   Telescopes that focus incident visible light by refraction through lenses.

7. What is the objective lens?

   The lens closest to the object that produces a real image.

8. What is the eyepiece lens?

   A converging lens closest to the eye that magnifies the image produced by the objective lens.

9. What is normal adjustment?

   When the emergent light rays are parallel, and the image is formed at infinity.

10. What is an object's angular size?

    The angle between the lines of sight of two opposite ends of the object.

11. What is the ray diagram two converging lenses in normal adjustment?

12. What is chromatic aberration?

    When an objective lens focuses the different wavelengths inside white light at a range of focal lengths and causes coloured edges to the image.

13. What is spherical aberration?

    Due to the curvature of the lens or mirror, the incoming light rays of a parallel beam focus at different positions.

14. What is an achromatic doublet?

    It is made up of two lenses that have a high and low level of dispersion to compensate for each other, and to cancel out the chromatic aberration.

15. What is the ray diagram for a Cassegrain arrangement?

16. What is the function of a parabolic mirror or lens?

    The shape of the mirror or lens is a specific shape that focuses all of the incident rays at a single point, removing the affect of spherical aberration.

17. What are the disadvantages of a refracting telescope?

    Heavy, difficult, and large.

18. What are the advantages of a reflecting telescope?

    Light, no chromatic aberration, small.