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Telescopes and Microscopes

Telescopes and Microscopes. Question:. When you look through the converging eyepiece of a telescope, you see an enlarged image of a distant object. If you replace the eyepiece with one having more curvature and a shorter focal length, will the image you see appear larger or smaller?.

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Telescopes and Microscopes

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  1. Telescopes and Microscopes

  2. Question: When you look through the converging eyepiece of a telescope, you see an enlarged image of a distant object. If you replace the eyepiece with one having more curvature and a shorter focal length, will the image you see appear larger or smaller?

  3. Magnifying Glasses • If the object distance is less than the focal length, no real image forms on the far side of the lens • The image distance is a negative number! • There still is an image, a virtual image • The virtual image forms on object-side of lens

  4. Virtual Images • Virtual images are • upright • larger than the object • more distant than the object • Images are magnified • The shorter the focal length of the lens, • the closer the object must be • the smaller the region on the object that is viewed • the more the magnification of the object

  5. Refracting Telescopes • One converging lens form a real image • A second converging lens forms a virtual image of that real image • Virtual image is highly magnified view of object, but inverted and flipped right-to-left

  6. Question: When you look through the converging eyepiece of a telescope, you see an enlarged image of a distant object. If you replace the eyepiece with one having more curvature and a shorter focal length, will the image you see appear larger or smaller?

  7. Mirrors 1 • Flat mirror forms virtual image • Virtual image is similar to the object

  8. Mirrors 2 • Concave mirror forms virtual image of near object • Virtual image is • upright • larger than object • more distant than object

  9. Mirrors 3 • Concave mirror forms real image of distant object • Real image is • Inverted and flipped left-to-right • Smaller or larger than object • On object side of mirror

  10. Mirror Telescopes • A concave mirror forms a real image • A converging lens forms a virtual image of that real image • Virtual image is highly magnified view of object, but inverted and flipped right-to-left

  11. Comparison • Refracting telescopes • Require clear glass parts • Require achromatic multi-element lenses • Mirror telescopes • Require stable but not necessarily transparent parts • Do not have any dispersion problems • Most small telescopes are refractors • Most large telescopes are reflectors

  12. Why Large Telescopes • Large aperture yields bright images • Diffraction limits resolution of telescope • Light travels as a wave • Passing through an aperture truncates wave • Wave spreads following truncation • Image points are smeared out • Larger aperture yields less diffraction

  13. Microscopes • Just like telescopes, except the object distance is much, much less than the image distance • First lens projects a real image • Second lens acts as a magnifying glass to examine the real image

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