Perhaps as much as 95 of the matter in superclusters is dark ...

[Mimi]

Perhaps as much as 95 of the matter in superclusters is dark matter.
 
  Indicate whether the statement is true or false

Question 2

Discuss several disadvantages of refractor versus reflector telescopes.
 
  What will be an ideal response?

[Kingjoffery]

Answer to Question 1

TRUE

Answer to Question 2

Refractors must use lenses, and thus all suffer from some chromatic aberration; mirrors reflect all wavelengths of light the same. Correcting for chromatic aberration means including more optical surfaces, requiring more work than any reflector design, which includes the secondary mirrors. Large refractor lenses must be supported by their edges, which means they will flex under their own weight. Mirrors can be built much larger, and supported from the back with no light blockage. Lenses require two precision surfaces; mirrors only need one. Thick lenses will absorb some light, which is not an issue for mirrors.

[Mimi]

Gracias!

[nguyenhoanhat]

TYSM