After taking an astronomy class, you purchase an astronomical telescope that has

Question

After taking an astronomy class, you purchase an astronomical telescope that has a focal length for the objective and eyepiece respectively of 196 cm and 1.21 cm. After using the telescope several times, you decide to increase its angular magnification by replacing the eyepiece. After replacing the eyepiece, the length of the barrel must be adjusted in order to bring objects into focus. Determine the best angular magnification you can obtain, if the barrel can only be shortened by 0.49 cm from its current length.

Explanation / Answer

Since the barrel length is shortened by 0.49 cm, the focal length of the new eye piece is:

fe = 1.21 - 0.49 = 0.72 cm

Magnification is given by:

M = fo/fe = 196/0.72 = 272.22

Hence, M = 272.22

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