Aldric Bek 3I301 Physics ACE

 Refraction occurs because light travels in different speeds in different media. In [pic 1], the bottom part of the light ray reaches the medium of higher optical density first, thus it slows down first, while the top part of the light is still moving at the speed of light in air, thus bending of the light occurs. [pic 1] 2

Most of the inventions made with the application of refraction involves lenses. Thus we will look at how lenses work before looking at the inventions made using refraction. 3

 Light in lenses follow the normal rules of refraction. It is the arrangement of the surface of the glass that gives it the converging and diverging properties. [pic 2] [pic 3] 4

1. The spectacles 2. The binoculars 3. The refracting telescope 4. The projector 5. Beam splitter (Image splitter) 5

 Importance: to correct imperfect eyesight (which most of us have).  The spectacles work by cancelling out the too strong/weak focus of the cornea in the eye.  For myopia (nearsightedness):  The light is focused too much, thus the lens diverge the light rays away from the centre of the eye to balance the offset of the eye’s lens.  For hyperopia (farsightedness):  The opposite of myopia stands. [pic 4] MYOPIA [pic 5] HYPEROPIA 6

 Important tool in warfare and observing wildlife.  The binoculars helps us see far objects by focusing the image onto our eyes with the help of lens. [pic 6] 7

 The objective lens is usually a biconvex lens.  This will cause the image to be inverted when viewing at the far objects.  The two prisms solve the above problem, by inverting the image again.  The eye piece is usually made up of more than one lens, often includes a biconvex and a negative meniscus lens. 8

 Used in studying astronomy.  Using lens to focus very far objects onto a smaller area for us to see the image of the object.  The light from the object is focused by the objective lens, which will converge near the focal length of the eyepiece, which will invert the image again for the eyes to see it upright. 9 [pic 7] A simple refracting telescope [pic 8] How does a refracting telescope works

 Used in schools/lectures for presentations and in cinemas for movies.  The image is inverted before it is projected, as when the image is magnified, it would be inverted from the projected image.  The projector allows the little light used in the image projector to become a large image for everyone to see, saving energy in a way. 10 [pic 9]

 Used in stereoscopy, or in producing 3D images (by having two images to create impression of depth).  Traditionally made up of two prisms with a layer separating the prisms, the thickness depends on what wavelength of light is supposed to exit straight through horizontally.  This is made possible by frustrated total internal reflection (occurs when a very thin layer (less than the wavelength of the light) of low R.I. material is between two materials, allowing the light to pass through the material). 11 [pic 10]

 [pic 1] (2010, March 2)  Refraction of Light. Retrieved (2010, March 2) from  Refraction. Wikipedia. Retrieved (2010, March 2) from  Lens (optics). Wikipedia. Retrieved (2010, March 2) from  [pic 2] (2010, March 2)  [pic 3] (2010, March 2)  How Do Glasses Work. eHow. Retrieved (2010, March 2) from  [pic 4] (2010, March 2)  [pic 5] (2010, March 2)  Stereoscopy. Wikipedia. Retrieved (2010, March 3) from  Total Internal Reflection. Wikipedia. Retrieved (2010, March 3) from  Interferometry. Wikipedia. Retrieved (2010, March 3) from  Beam splitter. Wikipedia. Retrieved (2010, March 3) from  Cragar. (2009, May 26). Re: what inventions (or other wise) use light refraction? [Online Forum Comment]. Retrieved from  Binoculars – How Binoculars Work?. AZOOptics. Retrieved (2010, March 3) from  [pic 7] (2010, March 3)  [pic 8] (2010, March 4)  Refracting and reflecting telescope. Thinkquest. Retrieved (2010, March 4) from  [pic 10] (2010, March 4) 12

“If light travelled at the same speed in all media, everyone would be blind”. 13