Images in Mirror and Lenses


General terms for forming images from lenses:

Images are:

  • Real if they occur on the opposite side of the lens as the object. (R)
  • Virtual if they occur on the same side of the lens to the object. (V)
  • Upright if they are the same way up as the object. (U)
  • Inverted if they are upside down. (I)
  • Diminished if they are smaller than the object. (D)
  • Magnified if they are larger than the object. (M)

General terms for forming images from mirrors:

Images are:

  • Real if they occur on the same side of the lens as the object. (R)
  • Virtual if they occur on the opposite side of the lens to the object. (V)
  • Upright if they are the same way up as the object. (U)
  • Inverted if they are upside down. (I)
  • Diminished if they are smaller than the object. (D)
  • Magnified if they are larger than the object. (M)

Note: Most terms are identical for lenses and mirrors except for real and virtual images.


Diagrams:

Drawing diagrams for lenses and mirrors is done to illustrate the magnitudes of various features. The features that are usually illustrated include:

u = the distance between the object and the lens/mirror.

v = the distance between the image and the lens/mirror.

{ h }_{ o } = the height of the object.

{ h }_{ i } = the height of the image.

f = the focal length of the lens/mirror.

M = the magnification of the image.


Equations:

The position and nature of the image formed by a lens is calculated using the lens formula:

\cfrac { 1 }{ f } =\cfrac { 1 }{ u } +\cfrac { 1 }{ v }

The size of an image can be determined using the formula for magnification. Magnification is a ratio of the image to the object:

M=\cfrac { { h }_{ i } }{ { h }_{ o } } =\cfrac { v }{ u }


The following simulation allows you to play around with a lenses and images.


Images formed by refraction in a convex lens:

Images formed by refraction in a concave lens:

Images formed by reflection in a concave mirror:

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