$refractor telescope$

$refractor telescope$

The size of an image produced by a lens is proportional to the focal length of the lens. The largest lens is called the objective lens, and the smaller lens used for viewing is called the eyepiece lens. Most refracting telescopes use two main lenses. This type of telescope is called a refracting telescope. They focus the light and make distant objects appear brighter, clearer and magnified. The earliest telescopes, as well as many amateur telescopes today, use lenses to gather more light than the human eye could collect on its own. This point is also called the focal point, and its distance is measured in negative units. The rays will then appear to originate from a point in front of the lens. If a lens is concave or diverging, it takes parallel rays and bends them so that they spread out. The distance from the lens to the focal point is called the focal length of the lens. If a lens is convex or converging, it takes parallel light rays from a distant object and bends them so that they converge to a single point called the focal point. They are ground so that their surfaces are either segments of spheres or planes. Lenses form images by refraction and are typically made of either glass or plastic. In the diagram below, light is leaving air and entering glass, so it bends towards the normal on the way in, and away on the way out of the glass. Light follows the same same principle and bends towards the normal when traveling into a medium with a higher index of refraction, and away from the normal when traveling into a medium where it can go faster. If the you approach the beach at an angle, one of the tires will be slowed down by the sand before the other is, and the car will turn in the direction of the tire that touched the sand first. If you approach the beach straight on, the car will slow down, but not change direction. Imagine driving a car from smooth pavement onto a sandy beach. The direction the light takes depends on whether it travels faster or slower in the new medium. If it enters at an angle, its speed and its direction will change. If light enters the new medium at a right angle to the surface, it will change speed, but not direction. Index of Refraction for Some Common Substances The higher the refractive index, the more light is slowed down by the substance. The refractive index of a medium is the ratio of the speed of light in a vacuum to the speed of light in the medium. For example, light travels more quickly through air than through water. The light that continues through the new medium will either speed up or slow down depending on how fast it can travel through each medium. When traveling from one medium to another, some light will be reflected at the surface of the new medium.

$refractor telescope$

Light travels at slower speeds through different materials, such as glass or air. Light travels through a vacuum at its maximum speed of about 3.0 × 10^8 m/s, and in a straight path.

$refractor telescope$

Refractor telescope