Interactive
Lecture Demonstrations
Prediction
Sheet—Image Formation with Lenses
Directions:
Click here to download the
Prediction Sheet where you will enter your predictions and answers. Write
your name at the top to record your presence and participation in these
demonstrations. For each demonstration
below, write your prediction on this sheet before making any observations. You
may be asked to send this sheet to your instructor.
Demonstration 1: You
have a converging lens. An object in
the shape of an arrow is positioned a distance larger than the focal length
to the left of the lens, as shown in the diagram on the right. Draw several rays from the head of the
arrow and several rays from the foot of the arrow to show how the image of
the arrow is formed by the lens. Is this a real or a virtual image? Only after you have made your prediction,
click to observe the images ImageFormation1a and 1b. These show two light bulbs, at the top and
bottom of the object, and a lens. Write any corrections to your prediction in
the space at the right. Now go to https://www.compadre.org/Physlets/optics/ex35_1.cfm
and click on Initialize part (c). Drag the point source up and down
on the object and describe how all of the rays from any point on the object
converge to a point on the image. Then go to https://www.compadre.org/Physlets/optics/ex35_2.cfm First click on converging lens and
then object with point sources. What happens to all the rays from the top of the
object? Bottom? Finally,
select ray diagram, and compare it to the one you
drew. |
|
Demonstration 2: What
will happen to the image if you block the top half of the lens with a card? Answer in words and show what happens on
the diagram on the right by making any changes needed in the rays you drew in
Demonstration 1. Only after you have made your prediction, observe the images ImageFormation2. Then write any
corrections to your prediction in the space at the right. |
|
Demonstration 3: What
will happen to the image if you block the top half of the object with a card? Answer in words and show what happens on
the diagram on the right by making any changes needed in the rays you drew
above for Demonstration 1. Only after you have made your prediction, observe ImageFormation3. Then write any
corrections to your prediction in the space at the right. How is this
different than Demonstration 2? |
|
Demonstration 4: What
will happen to the image if you remove the lens? Answer in words and show what happens on
the diagram on the right by making any changes needed in the rays you drew
above for Demonstration 1. Only after you have made your prediction, observe ImageFormation4. Then write any
corrections to your prediction in the space at the right. Now go to https://www.compadre.org/Physlets/optics/ex35_2.cfm First click on converging lens and then object with
point sources. Then
click on restart and then just object with point sources. How do the cases with the lens and without the lens differ? |
|
Demonstration 5: What will happen to the image if the object
is moved further away from the lens?
Will the position of the image change? If so, how? Will the size of the
image change? If so, how? Will the image be
real or virtual? Only after you have made your prediction go to https://www.compadre.org/Physlets/optics/ex35_3.cfm
Move the lens further from the
object, and then write any corrections to your prediction below. |
|
Demonstration 6: What will happen to the image if the object
is moved closer to the lens (but is still further away than the focal point)?
Will the position of the image change? If so, how? Will
the size of the image change? If so, how? Will
the image be real or virtual? Only after you have made your prediction use https://www.compadre.org/Physlets/optics/ex35_3.cfm and move the lens closer
to the object, and then write any corrections to your prediction below. |
|
Demonstration 7: What will happen to the image if the object
is moved closer to the lens so that it is closer to the lens than the focal
point? Will the position of the image change? If so, how? Will the size of the
image change? If so, how? Will the image be
real or virtual? Only after you have made your prediction go to https://www.compadre.org/Physlets/optics/ex35_3.cfm
and move the lens closer to the
object than the focal length, and then write any corrections to your
prediction below. |