Astrophysics

Question 1

What is a problem with reflecting telescopes?

Answer 1

Spherical aberration-images are blurry or unfocused because the mirrors are too rounded. Use a parabolic shaped mirror

Question 2

What are 4 parts that are key for a functioning refracting telescope?

Answer 2

Lens quality, lens diameter, angular magnification and normal adjustment

Question 3

What is chromatic aberration?

Answer 3

Glass refracts different colours by different amounts. The principal focus will be different for each colour so blurs the overall image.

Question 4

List disadvantages of refractive telescopes

Answer 4

-Glass can have impurities and bubbles of air absorbing some light, large lenses are very difficult and expensive to make.
-Large lenses are heavy and can only be supported by the edges so their shape can distort.
-To get good magnification the objective lens needs a long focal length making the telescope very long.
-Spherical aberration

Question 5

List advantages of reflectors

Answer 5

-No chromatic aberration as mirrors don’t refract light.
-No spherical aberration due to parabolic mirrors.
-No distortion as mirrors are better supported.
-Better resolving power/greater brightness.
-More light gets through as a lens absorbs more light

Question 7

What is an airy disk?

Answer 7

The 1st order maxima from an object diffracting through a telescope. 2 objects can appear overlapped through diffraction.