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: