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 .