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Optics
Chapter 15
What is Optics?
• The study of how light behaves
Uses:1. lenses (bend light)2. mirrors (reflect light) 3. prisms (separate light)
What are Light Rays?• Imaginary lines that follow single beams of light– Shows path of the wave– Is perpendicular to the wave front
• Light rays travel in straight lines– BUT change medium, direction of travel changes
Mirrors & Reflection
• A mirror shows an image that looks behind the mirror & flipped
• Rays reflected back at an equal but opposite angle
• The two rays with reflection: 1. Incident Ray: ray coming from object 2. Reflected Ray: ray bouncing off mirror
• The Law of Reflection – Light rays bounce off a mirror at the same angle at
which they arrive– Angles relative to the normal (perpendicular line)
– Example: if a ray came in at an angle 50° from the normal, it would be reflected at the same angle, 50°
Refraction & Lenses
• Refraction: light is bent as it travels from one medium and into different one
• Lenses – transparent materials that bend light
• Focal Point: Light rays enter a lens parallel to its axis and then bend to meet at focal point
• Focal Length: Distance from center of the lens to the focal point
• 2 kinds of lenses:1. Converging Lens: bend light rays toward the
focal point• Magnifies object
2. Diverging Lens: bend light rays outward, away from focal point
• Reduces object
What is an Image?
• All light rays are brought together at one point– Images differ from objects – • an object is real…an image is not
Types of Images• 2 Types1. Real Image – inverted image to right of lens– Object left of lens – Object distance greater than the focal length
• Ex) Our eyes: • we see objects upside down, our brain has to flip it
2. Virtual Image– Object & image are left of
lens – Compared to object, the
image is:1. smaller (closer to lens)2. bigger (far from lens)
– Ray don’t actually meet to make an image
– Ex)Magnifying glass, microscope, optical illusions
Works Cited
• Hsu Ph.D., Tom. Foundations of Physical Science. 1st ed. Peabody: Cambridge Physics Outlet, 2002. 255-266. Print.
• Microsoft Office PowerPoint ClipArt. 2000. • VirtualImage.png. 2012. Photograph.
WikipediaWeb. 23 May 2012. http://en.wikipedia.org/wiki/File:VirtualImage.png .