Which design yields an upright and magnified image?

Which design yields an upright and magnified image?

• A. Galilean
• B. Keplerian
• C. Reflecting
• D. Refracting

Answer: (A)

A Galilean telescope yields an upright and magnified image because the eyepiece is a diverging lens paired with a converging objective. The objective forms a real image at its focal plane, which is inverted, but the diverging eyepiece takes that image and produces a virtual image that the eye sees without flipping orientation. The result is magnified and erect. In contrast, designs using two converging lenses (like the Keplerian telescope) create a magnified image that is inverted, since the light undergoes two inversions. Refracting and reflecting systems without additional erecting optics also tend to form inverted images, so without extra components they do not produce an upright final image.

A Galilean telescope yields an upright and magnified image because the eyepiece is a diverging lens paired with a converging objective. The objective forms a real image at its focal plane, which is inverted, but the diverging eyepiece takes that image and produces a virtual image that the eye sees without flipping orientation. The result is magnified and erect.

In contrast, designs using two converging lenses (like the Keplerian telescope) create a magnified image that is inverted, since the light undergoes two inversions. Refracting and reflecting systems without additional erecting optics also tend to form inverted images, so without extra components they do not produce an upright final image.