CH 14: MIRRORS & LENSES 14.1: Mirrors

I. Plane Mirrors  Flat, smooth mirror  Creates a virtual image: an image your brain perceives even though no light rays pass through it.  Image appears upright and as far behind the mirror as the object is in front of it (same size as object).

How your brain sees it…  Your brain always interprets light rays as if they have traveled in a straight line.  It doesn’t realize the rays have reflected and changed direction.

Terms to Know  focal point: point on the optical axis of a concave mirror or convex lens through which light rays traveling parallel to the optical axis pass after striking the mirror or lens  optical axis: imaginary straight line perpendicular to the center of a concave mirror or convex lens  focal length: distance from the center of a mirror or lens to the focal point

II. Concave Mirrors  Mirror whose surface curves inward  Light rays converge (come together)

How Concave Mirrors Form Images  The image formed by a concave mirror depends on the object’s location relative to the focal point.  Concave mirrors can form real images: rays of light actually pass through the location of the image “projects” an image Occurs when object is past the focal point: Image of an object more than 2 focal lengths is real, upside down, and smaller than the object. Image of an object between 1 and 2 focal lengths is real, inverted, and larger than the object.

 Concave mirrors will form NO IMAGE when the object is held at the focal point.  Concave mirrors will form virtual images when objects are between the focal point and the mirror. Virtual image is upright and larger than the object (i.e. magnifying mirrors)

III. Convex Mirrors  Mirror whose surface curves outward  Light rays diverge (spread apart) after reflection  wide “field of view”  Forms a virtual image that is smaller than the actual image and is always upright.  Examples: back of a spoon, security mirrors at corners  “objects in mirror are closer than they appear”