1. REFRACTION AND ITS USES Done by: Wecom Huang Hui Kang 3P324

2. Refraction Refraction is the bending of light when it passes from one transparent medium to another with different optical densities. When light passes from an optically denser medium to an optically less dense medium (eg from glass to air), it bends away from the normal(an imaginary line perpendicular to the boundary of the two mediums). When light passes from an optically less denser medium to an optically denser medium, it bends towards the normal.

3. 5 Important Inventions  Magnifying Glass  Telescope  Microscope  Camera  Glasses/Spectacles

4. Magnifying Glass  A magnifying glass is normally made up of a handle, frame and a convex lens.  The convex lens produces a magnified, upright, virtual image.  The earliest magnifying glass dates back to 424BC.

5. How Magnifying Glass Works  Refraction occurs and the light rays from the object bend to form a magnified image, which can be seen by the eye. Thus an object can be seen more clearly.  The distance between the object and the convex lens must be shorter than the focal length of the convex lens for a magnified image to be produced.

6. Diagram

7. Magnifying Glass  With the use of a magnifying glass, people can see objects better as there is a magnified image. Observations can better be made and more details can be seen.  For example, magnifying glasses are a symbol and icon for detective fiction. Sherlock Holmes is well known for carrying a magnifying glass.

8. Telescope  A telescope is an instrument used to collect electromagnetic radiation so that faraway objects can be observed.  An optical telescope gathers and focuses light which are mainly from the visible part of the electromagnetic spectrum. Thus, optical telescopes are a subset of telescopes.  Galileo Galilei is widely known to be the first person to use a telescope for astronomical purposes.

9. How Telescopes Work  Telescopes contain lenses. Thus refraction of light occurs and the telescope makes use of this phenomenon to focus parallel light rays from very remote objects to form a sharper and clearer image.

10. Components

11. Diagram

12. How Telescopes Work  The parallel light rays from distant objects are gathered by a convex or concave mirror first. This is reflection.  This forms an image at the focal plane, which can be seen at the eyepiece.  This is where refraction comes in. The eyepiece acts like a magnifying glass, which makes use of refraction to form an inverted, virtual and magnified image.

13. Telescope  The discovery and use of telescopes are very important and essential to astronomy. Astronomers use telescopes to view and observe distant planets and galaxies. This has led to the huge development of astronomy and has greatly improved our understanding of the universe. Many planets in our solar system are discovered with the help of microscopes.  For example, when Galileo used the telescope, he discovered that the Earth revolved around the Sun, which was not what the people then thought. They believed that the Sun and everything else revolved around the Earth.

14. Microscope  A microscope is an instrument which allows people to view microscopic objects, which are objects that are invisible to the naked eye due to their small size.  Two eyeglass makers were recognized to be the inventors of the early microscope. They are Hans Lippershey and Hans Janssen. The microscope first appeared in Middelburg, Netherlands in the year 1590.

15. Microscope  Optical microscopes make use of a system of lenses to magnify images of small objects, also called samples.

16. Diagram

17. How Microscopes Work  The objective lens is actually a magnifying glass with a very short focal length (a few mm) so that when the sample is brought very close to the objective lens, a magnified, virtual image is obtained.  Refraction occurs at the objective lens, thus the microscope makes use of refraction to work.

18. Microscope  Microscopes are involved extensively in many fields such as nanophysics, microbiology, pharmaceutics research, biotechnology and microelectronics.  Microscopes were used to discover cells, the building blocks of life. Thus microscopes have contributed to our understanding of biology and how our bodies work.

19. Camera  A camera is a device that records images, still or moving (videos).  Cameras usually consist of the following parts: 1. Aperture 2. Recording surface 3. Lens 4. Shutter button 5. Etc.

20. How Cameras Work  Light from the object enters through the aperture.  The lens of the camera focuses the light onto the film/detector. This is refraction.  The image formed is diminished, real and inverted.

21. Diagram

22. Camera  The camera is a very important invention.  Evidences are sometimes recorded using a camera and thus cameras help to solve crimes.  Also, cameras play an important role in many people’s lives. Cameras help to record pictures and videos. They capture the situation at a particular time and brings back memories.

23. Spectacles  Many people around the world cannot see things clearly without the help of spectacles. They suffer from myopia (nearsightedness) or hyperopia (farsightedness).  Spectacles are frames with lenses worn in front of the eyes for vision correction and also eye protection.

24. How Spectacles Work  When a person suffers from myopia or hyperopia, his cornea is out of shape and light cannot be focused onto the retina, causing blurred vision.  The lenses of spectacles refract light from the surroundings into the retina of the eye. The spectacles help to refract the light correctly so that the light rays can meet at the retina, producing a sharp and clear image.

25. Diagram

26. Spectacles  The invention of spectacles has helped many people around the world to regain perfect vision.  Thus it is a very important invention that works on the principles of refraction.

27. References  http://en.wikipedia.org/wiki/Hyperopia http://en.wikipedia.org/wiki/Hyperopia  http://en.wikipedia.org/wiki/Myopia http://en.wikipedia.org/wiki/Myopia  http://en.wikipedia.org/wiki/Mammalian_Eye http://en.wikipedia.org/wiki/Mammalian_Eye  http://en.wikipedia.org/wiki/Eye http://en.wikipedia.org/wiki/Eye  http://en.wikipedia.org/wiki/Magnifying_Glass http://en.wikipedia.org/wiki/Magnifying_Glass  http://en.wikipedia.org/wiki/Camera http://en.wikipedia.org/wiki/Camera  http://en.wikipedia.org/wiki/Glasses http://en.wikipedia.org/wiki/Glasses  http://en.wikipedia.org/wiki/Telescope http://en.wikipedia.org/wiki/Telescope  http://en.wikipedia.org/wiki/Optical_Telescope http://en.wikipedia.org/wiki/Optical_Telescope

28. References  http://en.wikipedia.org/wiki/Optical_Microscope http://en.wikipedia.org/wiki/Optical_Microscope  http://en.wikipedia.org/wiki/Microscope http://en.wikipedia.org/wiki/Microscope  http://en.wikipedia.org/wiki/Refractive_Index http://en.wikipedia.org/wiki/Refractive_Index

29.  THE END