Real and Virtual lmages
Here is a way to remember real and virtual images with a convex lens.
a) What to do
- Get the A lens from your Optics
Kit.
- Place the magnifying lens over the drawing of an arrow.
- Hold the magnifying lens at about arm's length away from your eye,
and slowly lift the magnifying lens off the picture.
- Keep lifting the magnifying lens until the image you are watching
turns upside down.
- Repeat for the B image
b) What happened
As you first began to move the magnifying lens further away from the
page, the image grew larger. At one point the image became fuzzy and
then came back into focus upside down. This is because of the way the
magnifying lens bends the light traveling to your eye from the page.
When the magnifying lens is close to the page, you see what is known
as a virtual image. This is an upright image that is larger than
the image on the page. As you move the magnifying lens closer to your
eye and away from the page, you see what is called a real image,
which is upside down. Look at the diagrams below to see how the light
is bent by the lens to form the two types of images you saw.
c) Summary: If the object is inside the focal plane (F) the image is virtual
and erect; if the object is outside the focal plane (F) the image is real
and inverted.
Continue on to the
Optical Microscopy Readings
Page
Page authored by the ACEPT
W3 Group
Department of Physics and
Astronomy, Arizona State University,
Tempe, AZ 85287-1504
Copyright © 1995-2000 Arizona Board of Regents. All rights reserved.
|