The Reason That the Primary Mirror of an Astronomical Telescope

question 216

Multiple Choice

The reason that the primary mirror of an astronomical telescope is often shaped and polished to a parabolic shape is

• A) to avoid the chromatic aberration that would be produced by an equivalent spherical mirror.
• B) that it is lighter and easier to mount in a telescope because it requires less glass than an equivalent spherical mirror.
• C) that it is easier to produce, even though the resulting mirror will produce more spherical aberration than an equivalent spherical mirror.
• D) to avoid spherical aberration by bringing parallel rays to a single focus.

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