Telescopes Flashcards
What lenses are simple refracting telescopes made from?
Two lenses with different lens powers.
Objective lens
Eye lens- The stronger one
What is the purpose of the objective lens?
Collects light from the object being observed and forms an image of it.
What is the purpose of the eye lens?
Magnifies the image so we can see it.
Why are the lenses in a telescope aligned?
So their focal points are in the same place
Why are light rays parallel when they arrive on earth?
Because they have traveled so far from space.
What does the objective lens do to parallel rays?
It converges the parallel rays to form a real image between the two lenses.
What is the formula for calculating Magnification?
Magnification= Focal length of objective lens(f o)
divided by
Focal length of eye lens (fe)
What type of mirror do most astronomical telescopes use instead of a convex objective lens?
Concave mirror
What is the center of a mirror’s surface called?
A Vertex
Where is the centre of curvature found?
The mirror being like a part of a sphere the centre of the sphere is the centre of curvature
Where is the focal point from a concave mirror found?
Halfway between the centre of curavture and the vertex
Where do all these points lay, centre of curvature, vertex and focal point?
The axis.
What will happen to rays parallel to the axis when they shine on the concave mirror?
They will reflect and all meet at the focal point
What does putting an eye lens near the focal point of the mirror do?
Forms a magnified image.
