Presentation on theme: "Yu Zhuoxin 3P3 28. Refraction What does refraction mean ?"— Presentation transcript:
Yu Zhuoxin 3P3 28
Refraction What does refraction mean ?
Definition of refraction Refraction is the bending of light as it passes from one substance to another. The bending is caused by the differences in density between the two substances. Eg
Uses of refraction Camera Microscope Magnifying glass overhead projector Telescope …………
Camera The window--technically called the aperture--is covered with a ground-glass lens for focusing the light that enters the camera. Between the lens and the window is a shutter that opens to let light into the camera body. The photographic medium is the film on which the light image is recorded.
Camera-how do light refract? making an image To make the image, you need to use lenses, and fancier cameras have fancier lense systems to get better images. To actually get an image where the film is, the lenses take the incoming light and focus it there. A majority of cameras have a lens positioned in front of the camera's opening to gather the incoming light and focus all or part of the image on the recording surface. The light can be focused as light bents when they enters the lens. This is due to the reflection of light.
Microscope A microscope is an instrument to see objects too small for the naked eye, such as cells, bacteria and even atoms There are many different types of microscopes. Actually, some microscopes do not work on the phenomenon of refraction.
Microscope light waves being bent as they travel through glass. In a microscope, the idea is to bend diverging (spreading- out) light into a parallel path, then bend that parallel-path light into a small focus at the eye, and there is a magnitude image formed.
Microscope The object is placed between f and 2f. The total magnification is determined by the product of the magnification of the eyepiece and the magnification of the objective. The magnification of the eyepiece and the magnification of the objective must be calculated separately. There are two basic equations involved in finding the magnification. The first is 1/f=1/d i + 1/d o, and the second is d i /d o = s i /s o = magnification.
Magnifying glass A magnifying glass is simply a convex lens meant to be held up to an object to see it magnified. It is a very simple form of microscope.
how magnifying glass works The magnifying glass is not projecting an image onto anything; it is merely bending the Light rays from the object so that the object will appear larger. the object is between the center of the lens and F, and the image is magnified, virtual and upright, and on the same side. This is why a magnifying glass only works when it is close enough to the object (because the object must be between the center and F).
how magnifying glass works Eye sight Magnifying glass, namely convex lens image object
Telescope Telescopes are devices that are endowed with magnifiers to allow you to see things magnified with a clear view. Telescopes are commonly used in science or its branches, particularly astronomy and physics.
Telescope As the light rays travel through the lenses of the telescope, they are refracted. In a telescope, the idea is to bend parallel light from very faraway objects into a small focus at the eye so that a sharp and clear image can be formed at the back of the eye.
overhead projector An overhead projector typically consists of a large box containing a very bright lamp and a fan to cool it. On top of the box is a large fresnel lens that collimates the light.
overhead projector The light from the lamp travels through the transparency and into the mirror where it is shone forward onto a screen for display. The mirror allows both the presenter and the audience to see the image at the same time, the presenter looking down at the transparency as if writing, the audience looking forward at the screen. The height of the mirror can be adjusted, to both focus the image and to make the image larger or smaller depending on how close the projector is to the screen.