Refracting telescope: An astronomical telescope has an objective of diameter 20 cm with a focal length of 180 cm. The telescope is used with an eyepiece of focal length 30 mm. What is the angular magnification of this telescope?

Question

Quizplus · Accepted Answer

The angular magnification of a telescope is given by the formula:

m = -fo/fe

where fo is the focal length of the objective and fe is the focal length of the eyepiece.

In this case, fo = 180 cm and fe = 0.03 cm (since 30 mm = 0.03 cm).

So,

m = -(180 cm)/(0.03 cm)

m = -6000

Since angular magnification is a ratio, the negative sign just indicates that the image is inverted. So, the absolute value of the magnification is:

|m| = 6000

Therefore, the angular magnification of this telescope is 60x.

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