magnifications in mirrors & lenses. a measure of how much larger or smaller an image is...

Magnifications in Mirrors & Lenses

A measure of how much larger or smaller an image is compared with the object itself.

Magnification = image height or image distance object height object distance

M = hi or M = - di ho do The numbers can be obtained by measurement with a ruler

or be given to you Magnification does not have any units but make sure you

use the same units for height or distance!

OBJECTIMAGE

hi

MIRROR

dido

Parameters

ho

NOTE: positive and negative signs are used to give information about direction in physics

di is negative if you have a virtual image

If your image is inverted then height and magnification are NEGATIVE

Orientation of image with respect to object

Sign of M Type of image

Upright+

Virtual

Inverted-

Real

A concave shaving mirror has an object that is 93 cm tall placed in front of it. The image produced is upright and 51 cm tall . What is the magnification of the mirror?

A pencil is placed 25 cm in front of a concave mirror. It produces an inverted image that is 12.5 cm from the mirror. What is the magnification of the mirror?

A mirror has a magnification of 15. If the object placed in front of it is 2cm tall, what is the height of the image?

The magnification of a mirror that produces an inverted image is 7. How far away was the object placed from the mirror if the image produced is 2.5 cm away?

A thin lens is a lens with a thickness (distance along the optical axis between the two surfaces of the lens) that is negligible compared to the radii of curvature of the lens surfaces. 

Lenses whose thickness is not negligible are sometimes called thick lenses.

Thin lens equation= 1/f = 1/do +1/di