Factors Affecting Telescopes

Refracting Telescopes work by refracting the light rays going in through the telescope. This phenomenon is called refraction. Refraction occurs because light changes speed when it moves from one medium into another. Mediums are regions that’ll allow waves to travel through it, mediums like air, water, glass, and more, each have a reflective index. Each mediums have varying refractive indexes, the higher the refractive index, the more light is slowed down due to the medium.

Refractive Indexes in some Common Substances

Substances : Index of Refraction : Vacuum Air Water Perspex™ Crown Glass Oil Diamond 1.000 1.0003 1.333 1.495 1.517 1.518 2.417

The speed of light in a vacuum is 2.998 (rounded to 3)

This causes the wavelengths to decrease and light to ‘slow’ down and change direction, making the light ray’s angle of incidence greater than the angle of refraction.

However when light exits the objective lens and into the air, a medium with a lower refractive index, the light rays to go back into ‘normal speed’ the same speed it had before it entered the objective lens, causing the ray's’ angle of incidence to be smaller than the angle of refraction in terms of the normal in the interface of the back of the lens and the air/space in the telescope.

The light refracts again as it enters from air into the glass eyepiece lense, going through a more denser medium. Now the eyepiece lens is sometimes a convex lens like the objective lens but it could also be a concave lens, each guiding the light rays in similar paths through the telescope and into your eye. The light rays will then refract again away from the normal as they exit the eyepiece lens and into your eye, meaning light will enter a less dense medium : glass back into

2= sin-1(n1sin1)n2 2= sin-1(1sin(30)1.33 2=22.082 22 Magnification :

Hyper Physics - The Astronomical Telescope

Youtube - The Astronomical Telescope Magnification is a process about enlarging an object as well as a measurement of how enlarged an object has become. When the light rays from an object go through a lens or lenses, they magnify, and causes the image it creates to be bigger than the object.

Now in a refracting telescope the objective lens is slim and the eyepiece lens is usually much thicker. These two lenses are set up in a way that the focus of both lenses occur at the same point with focal length of the objective lens being greater than the focal length of the eyepiece