Now You See It

Marion White and Alex TreserPeriod 8/9 AP Physics 1

Types of Telescopes

Refracting telescopes work by using two lenses to focus the light and make it look like the

object is closer to you than it really is. Both lenses are in a shape that’s called 'convex'. Convex lenses work by bending light inwards (like in the diagram). This is what makes the image look smaller.

Reflecting telescopes, on the other hand, don’t use lenses at all. Instead, they use mirrors to

focus the light together. In this case, the type of mirror that they use is a concave mirror. Mirrors of this shape also accomplish the goal of bending light together, except that they do it by reflecting the light instead of bending it as it passes through (like lenses do)

“Object are Closer Than They Appear”

Light bounces off the flat surface, the angle of the reflected light is equivalent to the angle at which it struck the surface. The focal point- where the incoming light strikes the surface. Passenger side mirror is usually convex which extends the focal point so that the light striking the curved surface from a wider swath of angles all converge at the same focal point and then bounce into your eye.

Wider focal point compresses the reflected image which make the objects appear smaller.

Focal Lengthhttp://www.education.com/science-fair/article/upside/

Inverted L with lenses and flashlighthttp://www.education.com/science-fair/article/upside/

Why?

Magnifying glasses are made of convex lenses. A convex lens makes objects look larger because it disperses light. When objects are magnified, they are within the focal length of the magnifying glass. The focal length is the distance between the center of the lens and its focus, the point where an object can be viewed clearly through a lens.

Why can’t we see far away?As an object gets further away less of its light will reach your eye. The image takes up less space on your retina (the light-sensitive tissue at the back of your eye), making the image smaller. This makes details of the image harder to see.

To make a distant object appear brighter and larger, we effectively need a bigger eye to collect more light. With more

light we can create a brighter image, we can then magnify the image so that it takes up more space on our retina.

The big lens in the telescope (objective lens) collects much more light than your eye can from a distant object and

focuses the light to a point (the focal point) inside the telescope.

A smaller lens (eyepiece lens) takes the bright light from the focal point and magnifies it so that it uses more of your

retina.

Mirror Equation

f = focal length

d0 = object distance

di= image distance

Magnification Equation

di= image distance

d0= object distance

I= image size

O= object size

Convering lense

Divergent Lens

Two Converging Lenses

Converging and Diverging Lense