# Essay On Telescope

1193 Words5 Pages
What is a Refractor telescope?

A refracting telescope is a type of optical telescope, that magnifies objects from far away. It does this by refracting the light rays it collects to create an image that is inverted and thus magnified.

There are many different types of telescopes but most have the same parts to them. Refracting telescopes have two convex lenses:
The Objective lense - this lense has a greater diameter than the second lense as the greater the aperture, the more light it can collect and bring into focus at the focal point.
The Eye Lens - this is where the viewer can view the final image.

How does the telescope work?
Telescopes work by manipulating light waves and using properties of lenses
Refracted ray bends away from normal as it is moving faster

In order to find the angle of refraction, the angle of incidence or the refractive index of either mediums, we can use “Snell’s Law”

N1sin(theta sign)1 = N2sin(theta sign)2

where N is the refractive index of the medium
Theta is the angle in regard to the normal for that medium

and as long as you have 3 of 4 of the values, you are able to find the 4th. For example:

However there is one exception where rays will not refract when hitting a lense. This is when a ray of light hits the lense and causes the angle of refraction to be exactly 90 degrees. This is called the critical angle.

The angle of refraction can't be greater than 90 degrees, therefore if the angle of incidence is adjusted past the critical angle the light cannot refract out of the first medium and it becomes trapped. This causes a “Total Internal Reflection.” This describes when the boundary between the two medium acts as a mirror and the angle of incidence equals the angle of reflection. Total Internal Reflection can also only occur when light travels from more optically dense medium to a less optically dense medium. This is due to the ray of refraction bending towards the normal when going from less dense to more dense medium. The largest angle is just less than 90 degrees, so no angle of incidence could create and angle of refraction larger than or equal to 90