What is the magnification formula for a telescope?

Study for the NBEO Physiological Optics Test. Prepare with flashcards and multiple-choice questions, each question has hints and explanations. Ace your exam!

Multiple Choice

What is the magnification formula for a telescope?

Explanation:
The key idea is that telescope magnification is about how the eye’s viewing angle is scaled by the optics. For small angles, the angular size an object subtends is proportional to its height divided by its distance. The object, at distance Dobj from the objective, subtends an angle roughly h/Dobj. The eye through the eyepiece sees the image under an angle roughly proportional to h divided by the eye–eyepiece distance Doc. The telescope transfers the object’s angular information and scales it by the optics, so the resulting angular magnification is proportional to Doc/Dobj. In this convention, the magnification is thus M = Doc / Dobj, with the sign indicating whether the image is inverted or upright. So the ratio of the distance from the eye to the eyepiece to the distance from the object to the objective determines how much larger the image appears through the telescope.

The key idea is that telescope magnification is about how the eye’s viewing angle is scaled by the optics. For small angles, the angular size an object subtends is proportional to its height divided by its distance. The object, at distance Dobj from the objective, subtends an angle roughly h/Dobj. The eye through the eyepiece sees the image under an angle roughly proportional to h divided by the eye–eyepiece distance Doc. The telescope transfers the object’s angular information and scales it by the optics, so the resulting angular magnification is proportional to Doc/Dobj. In this convention, the magnification is thus M = Doc / Dobj, with the sign indicating whether the image is inverted or upright.

So the ratio of the distance from the eye to the eyepiece to the distance from the object to the objective determines how much larger the image appears through the telescope.

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