Tag: physics

Questions Related to physics

Which of the following is true for a telescope?

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  1. Final image is real and inverted.

  2. It increases the size of the object.

  3. It increases the angle subtended by image at the eye of the observer.

  4. Smaller telescopes are more powerful

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Correct Option: C
Explanation:

Telescope increases the visual angle of an object considerably and hence it allows to study the details of the objects carefully. The final image is actually much smaller than the object itself. 

In an astronomical telescope the focal lengths of objective and eyepiece should respectively be :

physics observing space: telescopes space research and satellites space travel space exploration and forms of light

  1. large and small

  2. small and large

  3. equal

  4. too small are too large

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Correct Option: A
Explanation:

In an astronomical telescope, two convex lenses are used for different focal lengths. In which the lens with large focal length is an objective lens which is used to see large distance objects like stars or planets and the one with small focal is eyepiece. Hence correct option is A.

The image formed by the telescope in normal adjustment position is at :

physics observing space: telescopes space research and satellites space travel space exploration and forms of light

  1. $D$

  2. $2D$

  3. $F$

  4. $\text{Infinity}$

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Correct Option: D
Explanation:

The image formed by the telescope in normal adjustment position is at infinity, so, that we can look at distant objects such as a star, a planet etc. Hence option D is correct.

While viewing a distant object with telescope a housefly sits on objective lens. Then which of the following is the correct statement :

physics observing space: telescopes space research and satellites space travel space exploration and forms of light

  1. housefly will be seen enlarged in image

  2. housefly will be seen reduced in image

  3. intensity of image will be decreased

  4. intensity of image will be increased

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Correct Option: C
Explanation:

When housefly sits on the objective lens, light intensity will fall at objective because housefly will stop the light to fall on the objective. So, intensity of the image is decreased. Hence correct option is C.

First adjustment of a spectrometer is :

physics observing space: telescopes space research and satellites space travel space exploration and forms of light

  1. focusing the distant object

  2. focusing the cross wires

  3. focusing the slit

  4. focusing near objects

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Correct Option: B
Explanation:

First we look through the telescope at any light - coloured surface and push the eyepiece in and out until we can see the cross-wires sharply, without straining our eyes, So, first adjustment in a spectrometer is focusing of the cross wires.

A terrestrial telescope is used to view the details of the distant objects on the earth.

physics observing space: telescopes space research and satellites space travel space exploration and forms of light

  1. True

  2. False

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Correct Option: A
Explanation:

Telescope used to see distant object in earth are Terrestial telescope.

Large aperture objective is used in telescopes as it helps in

physics observing space: telescopes space research and satellites space travel space exploration and forms of light

  1. increasing the brightness of image

  2. reducing image size

  3. increasing field of view

  4. increasing intensity by gathering more light

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Correct Option: A,D
Explanation:

The larger the objective, the more light the telescope collects and increases the brightness of image .

The field of view of the telescope decreases as the aperture increases, but the resolving power increases.
The objective lens of a telescope forms an real image of the night sky, the size of that image is in proportion to the focal length of the objective lens. It increases with increase in size of objective lens.

Large astronomical telescopes always use as objective

physics observing space: telescopes space research and satellites space travel space exploration and forms of light

  1. lens

  2. mirror

  3. combinations of lenses

  4. none of the above

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Correct Option: C
Explanation:
Large astronomical telescopes always use combination of lens as objective because
(1)To minimize spherical aberration.
(2)To maximize the amount of light ray entering the telescope.
(3)To optimize the quality of image.

In astronomical telescope, the final image is formed at:

physics observing space: telescopes space research and satellites space travel space exploration and forms of light

  1. the least distance of distinct vision

  2. the focus of objective lens

  3. the focus of the eye lens

  4. beyond the focal length of eyepiece.

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Correct Option: D
Explanation:

In astronomical telescope, the image formed by objective $I _1$ is real and inverted. It is formed at focus of objective lens. $I _1$ is placed between the focal length of eyepiece and the lens. Hence, it forms a virtual image beyond the focal length of eyepiece.

In which of the following instruments is final image erect?

physics observing space: telescopes space research and satellites space travel space exploration and forms of light

  1. Simple mircoscope

  2. Compound mircoscope

  3. Astronimical telescope

  4. None of the above

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Correct Option: A
Explanation:

A simple microscope is magnifying glass, an ordinary double convex lens having a short focal length that produces virtual and erect image.

rather a Compound microscope and astronomical telescope produces virtual and final inverted image. hence correct option is A.