Part I: Looking at Curved Mirrors
Please wait for the animation to
This first exercise explores the difference between real and virtual images (position is given in meters and
angle is given in degrees).
- Drag the object back and forth. In this animation when the image is on the left of the
mirror it is a real image, but when it is on the right it is a virtual image.
Place the object so that the image is to the right of the mirror (a
virtual image). Now let's identify where your eye/brain thinks the light
is coming from. First note that you (or your eye/brain) think light
travels in a straight line. Furthermore, when light diverges from
a point, your brain assumes that the point it diverges from (the image point)
is where the light originated. If your eye is where the eye is in the
diagram, where does your eye/brain think the light is coming from?
- Now consider a real image. Place the object at some point so that
the image forms somewhere in front of the eye. Where does the eye think
the light comes from?
- What does the eye see? (Is the image upright or inverted, bigger or
smaller than the object?)
- Move the object so that the image point is beyond the eye. (Notice
that for this case the light doesn't seem to have a convergence point so you'd
see a blurry image.)
- Considering the above cases, in which of them is the light actually
traveling through the image point?
For real images, the light actually travels through the image point. If
you put up a screen at the point where the rays cross, then a real image can be
formed on the screen, whereas if you put up a screen at the point of a virtual
image, you won't see anything on the screen (the screen is behind the mirror).
Original exercise: Exploration 33.2 in Physlet Physics
Original credits: Exploration by Anne J. Cox.
© 2004 by Prentice-Hall, Inc. A Pearson Company