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25 Cards in this Set
- Front
- Back
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Spherical Aberration |
Rays parallel to the principle axis that are farther from the principle axis are brought to focus at the different pts from those near center of the lens so the image is blurred. Pincushion effect or barreling effect. |
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Solution of spherical aberration |
Reduce the aperture |
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Angular Magnification |
The ratio of the angle subtended at the eye by the image to the angle subtended at the eye by the object M=∅i/∅o |
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Near point |
The nearest point in which the unaided eye can focus which is about 25cm |
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Chromatic aberration |
Different amount of refraction for different colors |
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Solution for chromatic aberration |
Achromatic doublet, lens of 2 materials |
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The large concave mirror in most reflecting telescopes is parabolic rather than spherical. Suggest one reason for this. |
With the use of parabolic mirrors the problem of spherical aberration is eliminated |
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State one advantage of reflecting telescopes compared to refracting telescopes. |
1) No chromatic aberration 2) Easier/cheaper to make large mirrors than large lens 3) Easier to support so they can be large 4) Less absorption in glass |
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Outline how the introduction of these telescopes have changed our view of the universe. |
A comparison of optic and non-optical images can be made and therefore our knowledge of what exists in the universe is drastically increasing |
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Telescope Magnification |
Fo/Fe |
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∅i |
The angle subtended by the eye at the image (eyepiece). Hi/f |
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∅o |
The angle subtended by the eye at the image (objective lens). Ho/D |
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Hi/Ho = _ at infinity |
∞ |
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Linear magnification of a microscope |
Mo(Me) |
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Focal point of converging lens |
It is a point in the principle axis where all rays pass through after passing through the lens. |
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State where the object should be placed if the image is to be formed at the far point. |
At the focal point, the far point is infinity |
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Spherical Mirrors: For a convex mirror the image is __________. |
Always upright, virtual, and smaller |
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Spherical Mirrors: If an object is inside the focal point then _________. |
It's image will be upright, virtual, and larger. |
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Spherical Mirrors: If an object is outside the center of curvature of a concave mirror then __________________. |
It's image will be inverted, real, and smaller. |
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Thin Lens: For a diverging lens the image is ____________. |
Always upright and virtual. |
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Disadvantages over refracting telescopes |
1) the mirror is vulnerable to damage and must be cleaned 2) the alignment of the mirror is easily shifter during movement of the telescope 3) the head observer or camera can easily block light traveling along the tube and therefore it reduces the benefit of a large mirror being used |
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Newtonian reflecting telescopes |
Uses a second mirror to transfer image from the inside to outside of the tube. Since plane mirror is high quality it introduces little to no distortion and is cheap. |
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Cassegrain reflecting telescopes |
Uses hyperbolic mirror as the second mirror, which allows the rays to pass through a hole in the surface of the primary mirror. This allows the observer to be in line with the telescope looking directly at the object being observed. Focal length can be longer hit 2nd mirror cuts off light and 1st mirror loses reflecting surface |
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Disadvantages of earth bound satellites |
1) light pollution from various sources 2) fixed telescope can only view sky in front of it 3) a steerable telescope can only view entire hemisphere of where it's located 4) many wavelengths of stars are absorbed by the atmosphere |
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Disadvantages of radio telescope |
Moving the large dish to point at objects in the sky can cause the parabolic shape to become deformed during the movement due to its weight. Loss of movement if it's in the ground |
