You are designing a refracting telescope to take a closer lookat astronomical ob
ID: 1756757 • Letter: Y
Question
You are designing a refracting telescope to take a closer lookat astronomical objects. In a refracting telescope, the objectivelens (lens closest to the object being viewed) forms areal image of the distant object inside thetelescope. This image is viewed through a second lens, theeyepiece, which forms an enlarged virtual image inthe manner of a simple magnifier.
You have two lenses available: lens 1 with focal lengthf1 = 55 cm and lens 2 with focal lengthf2 = 5 cm.
(a) Which lens should you choose for the objective?
Answer as follows: 1 if lens 1 should be chosen as theobjective; 2 if lens two should be chosen.
Objective lens =
(b) What will the overall length L of the telescope beif the final image (one formed by the eyepiece) is far away(effectively infinity) from the eyepiece ?
L = cm
(c) What angular magnification does your telescope provide?(Angular magnification is defined as the ratio of the angular sizeof the final image of the object formed by the telescope to theangular size of the distant object viewed with the un-aided eye.)Give a positive answer.
M =
(d) By reducing the spacing between the objective and theeyepiece, you can bring the final image created by the telescope toa distance of 25 cm behind the eyepeice, the "near point for anormal eye". (See textbook. p. 946 for a discussion of the nearpoint.) What is the spacing L' between the lenses thatcorresponds to this configuration?
L' = cm
(e) The configuration described in part (d) results in aslightly greater overall magnification. Calculate the new angularmagnification.
Explanation / Answer
given f1 = 55cm f2 = 5cm lens 1 taking as a objective lense f1= f0 length of telescope = L = f1+f2 =f0+fe angular magnification M = -f0/fe angular magnification M = -f0/feRelated Questions
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