Homework #6 The Thin Lens Equation
Please answer all questions completely. If calculations are required, show enough steps so that I can follow your reasoning.
1. Define:
a) real imageb) virtual image
c) spherical aberration
d) chromatic aberration
2.)
a. An object 1 cm high is placed 10 cm in front of a thin lens with a
focal length of 5 cm. Where is the image and what is its
magnification? Is the image real or virtual? Is the image upright or
inverted? (Note that this is the same problem you solved last week
using a ray diagram!)
b. Repeat Problem #1 assuming that the object is placed 3 cm in front
of the same lens. Again, find the image distance, magnification, and
tell if the image is real or virtual, upright or inverted.
3.
a. Repeat Problem #2 for the same object placed in front of a
diverging lens of focal length -5 cm. Find the image distance,
magnification and type of image when the object distance is 10 cm
from the lens and when it is 3 cm from the lens.
b. Can a diverging lens ever form a real image? Why or why
not?
4. Go to the web site http://webphysics.davidson.edu/Applets/Applets.html
Note: This is a Java applet and will not run in Chrome. As of 2013 it runs in Firefox. You may need to allow an exception
Notice that the x and y coordinates of the cursor appear in a box at
the lower left of the applet. Choose a lens- it will appear with a
focal length of 0.5 (we'll assume the unit is meters). Move the lens
to a position x=1.25
Next, choose an object. Move the object to the left of the applet screen (as close to x=0 as you can) and shorten it (grab the arrowhead and pull down) until it is around 0.5 units high. Note that the image appears at around x = 2.1 meters (as it should: you can verify that the object distance is about -1.25 m so the image distance should be about 0.85 cm.) Note that the image has a "1" located near it- it is the image of the first lens.
Now choose a second lens, also with focal length 0.5 meters. Place this at the x=3 m position. The image formed by the first lens is the object of the second lens. The image formed by the second lens has a numeral "2" located near it.
Questions to answer:
a. What type of image (real/virtual,
upright/inverted) does the first lens form?
b. What type of image (real/virtual, upright/inverted) is formed by
the second lens?
Now move the second (right hand) lens toward the first lens. Note what happens as the focal point of the second lens crosses the position of the image of the first lens! Place the second lens at the x = 2.5 m position.
c. What type of image (real/virtual, upright/inverted) is now formed by the second lens?
This is a microscope- the first lens is the objective and the second lens is the eyepiece.