Optical Instruments: Telescope

An astronomical telescope uses two lenses of powers 10 D and 1 D.Its magnifying power in normal adjustment would be:

The expression for astronomical telescope magnifying power is

Draw a labelled ray diagram of a reflecting telescope. Mention its two advantages over the refracting telescope.

Draw a schematic labelled ray diagram of a reflecting type telescope and The objective of a telescope is of larger focal length and of larger aperture (compared to the eyepiece). Why? Give reasons.

State the conditions for the phenomenon of total internal reflection to occur. 

Draw a labelled ray diagram of a reflecting telescope. Mention its two advantages over the refracting telescope.

An astronomical telescope has a converging eyepiece of focal length $5 \mathrm{cm}$ and an objective of focal length $80 \mathrm{cm}$ . When the final image is formed at the least distance of distinct vision$\left(25 \mathrm{cm}\right)$, the separation between the two lenses is

An observer looks at a tree of height $15 \mathrm{m}$ with a telescope of magnifying power $10$. To him the tree appears

Large aperture of telescope are used for

An observer looks at a distant tree of height $10 \mathrm{m}$ with a telescope of the magnifying power of $20$. To the observer, the tree appears as

A telescope has an objective of focal length $50 \mathrm{cm}$ and an eye piece of focal length $5 \mathrm{cm}$ The least distance of distinct vision is $25 \mathrm{cm}.$ The telescope is focussed from distinct vision on a scale $200 \mathrm{cm}$ away. The separation between the objective and the eye-piece in $\mathrm{cm}$ is, if final image is formed at least distance of clear vision:-

How many lenses are in a Galileo's telescope?

A astronomical telescope has objective and eyepiece of focal lengths $40 \mathrm{cm}$ and $4 \mathrm{cm}$ respectively. To view an object $200 \mathrm{cm}$ away from the objective, the lenses must be separated by a distance :

The magnifying power of a telescope is $9 .$ When it is adjusted for parallel rays, the distance between the objective and eyepiece is $20 \mathrm{cm}$. The focal length of lenses are :

A small telescope has an objective of focal length$144 \mathrm{cm}$ and an eyepiece of focal length $6.0 \mathrm{cm}.$ What is the magnifying power of the telescope? What is the separation between the objective and the eyepiece? The final image is formed at infinity.

The focal length of the objective and eye-piece of a telescope are respectively $100 \mathrm{cm}$ and $2 \mathrm{cm}.$ The moon substends an angle of $0.5°$ at the eye. If it is looked through the telescope, the angle subtended by the moon's image will be

Assertion : In an astronomical telescope, the objective lens has more aperture diameter

Reason : If we increase the focus distance of the objective lens, the magnification power of the telescope increases

In a small telescope, the focal length of the objective lens and eye-piece are respectively $144 \mathrm{cm}$ and $6 \mathrm{cm}.$ For the normal configuration, the magnification power and the length of the telescope tube are respectively :-

The focal length of the objective and eye piece of an astronomical telescope is respectively $100 \mathrm{cm}$ and $2 \mathrm{cm}$. The moon subtends an angle of $0.5°$, the angle subtended by the moon's image will be

When a material is used in a magnetic field $B,$ a magnetic moment proportional to $B$ but opposite in direction is induced. The metal is