Astrophysics L1.2 Refracting Telescopes

'Normal Adjustment' of a refracting telescope is when ...

• The Normal is perpendicular to the principal axis

• The distance between the objective lens and it's focal point equal the eyepiece focal length

• The distance between the lenses equals the sum of their focal lengths

• The distance of the observer to the eyepiece equals the distance between the lenses

We make the approximation that ...

• Light rays from the object are parallel at the telescope

• Light rays are coming from at least 1 parsec away

• Light rays are not affected by Earth's atmosphere

• Light rays will form a perfect image on our screen

For angular magnification we use the equation

•  $=\frac{f_e}{f_o}$  

•  $=\frac{f_o}{f_e}$  

•  $=\frac{2\alpha}{\beta}$  

•  $=\frac{2\beta}{\alpha}$  

The relationship between the collecting power of a telescope is ...

• proportional to the square of the eyepiece diameter

• proportional to the magnification squared

• proportional to the magnification

• proportional to the square of the objective diameter

The image seen through the eyepiece of a refracting telescope is ...

• Real

• Virtual

• Upright

• Reduced

Objects sufficiently distant can be considered to be ...

• Stars

• Points of light

• A variety of things

• Nebulae

What approximation do we make to obtain the magnification equation

•  $Sin\ \alpha=\alpha$  

•  $Cos\ \alpha=\alpha$  

•  $Tan\ \alpha=\alpha$  

•  $Tanh\ \alpha=\alpha$  

How many lenses are required for a refracting telescope

• 2

• 3

• 4

• 5

Refracting Telescopes require a construction like this ....

• Object, Small focal length convex objective , long focal length concave eyepiece, observer

• Object, Small focal length concave objective, long focal length convex eyepiece, observer

• Object, Long focal length concave objective, Small focal length convex eyepiece, observer

• Object, Long focal length convex objective, Small focal length convex eyepiece, observer