Images III

PREFLIGHT

Please type your (first) name:

Please type your LAST NAME and LAST FOUR SS# digits:

IN:

The following three questions refer to the material you were to read in preparation for the lesson. Questions one and three require you to write a three or four sentence response. Number two is a multiple choice question. Click in the appropriate circle.

You may change your mind as often as you wish. When you are satisfied with your responses, click the SUBMIT button at the bottom of this page. Don't submit more than once. (If you absolutely HAVE to resubmit it, put a note on the end to that effect.)

1.

From the discussions in class, or talking to a amateur astronomer, explain why Newtonian (reflecting) telescopes are much more common than Galilean (refracting) telescopes. It isn't just the price, because you can find cheap versions of both. Compare and contrast the advantages/disadvantages of mirrors vs lenses. A web site that may help is: http://www.optcorp.com/infotel2.htm

2.

Which of the following characteristics of a Newtonian telescope improve when the mirror is made larger? (1) Magnification increases; (2) Resolution or resolving power is better; (3) Spherical aberration is reduced; (4) Chromatic aberration is reduced.

1 and 2

3 only

All

None

3.

A light source is located to the left of a lens. You can click-drag the lens to any position. Find the focal length of the lens. Start

(Okay, if you really want it, here's some help)

honors extra

Why is it that the highest magnification of an optical microscope (say, above 400x) is done with an "oil immersion lens"? That is, a drop of oil is put on the sample, and the microscope objective is submerged into the drop. Wouldn't the oil have a higher index of refraction than air and reduce the magnification of the lens? What physics is making the oil necessary? The applet below may help.

The refractive index of the imaging medium is very important to the working numerical aperture of an objective. This applet explores how changes in this refractive index value can affect how light rays are captured by the objective. To operate the applet, move the slider to adjust the refractive index (N) of the imaging medium. The six hypothetical light rays emanating from the specimen pass through the cover glass, but only three are refracted into the objective at the lowest N value. The other three are reflected back into the cover glass. As the N (refractive index) value of the imaging medium is increased by moving the slider to the right, successively more light rays are able to refract into the objective until at the highest N value, all six rays enter the objective.

Below is a space for your thoughts, including general comments about today's assignment (what seemed impossible, what reading didn't make sense, what we should spend class time on, what was "cool", etc.):

You may change your mind as often as you wish. When you are satisfied with your responses, click the SUBMIT button.

I received no help from anyone on this assignment.