Optical Instruments

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

The expression for magnifying power of compound microscope is

The expression for astronomical telescope magnifying power is

The focal lengths of the objective and the eye piece of a compound microscope are $2.0 \mathrm{cm}$ and $3.0 \mathrm{cm},$ respectively. The distance between the objective and the eye piece is $15.0 \mathrm{cm}.$ The final image formed by the eye piece is at infinity. The two lenses are thin. The distance in $\mathrm{cm}$ of the object and the image produced by the objective, measured from the objective lens, are respectively

A convex lens $\mathrm{A}$ of focal length $20 \mathrm{cm}$ and a concave lens $\mathrm{B}$ of focal length $5 \mathrm{cm}$ are kept along the same axis with a distance $\mathrm{d}$ between them. If a parallel beam of light falling on $\mathrm{A}$ leaves $\mathrm{B}$ as a parallel beam, then $\mathrm{d}$ is equal to _________ $\mathrm{cm}$.

Total magnification of compound microscope is $20$ while magnification for eye piece is $5$. If final image is formed at near point which is taken $20 \mathrm{cm}$ then focal length of eye piece is

The focal length of magnifying glass is $25 \mathrm{cm}$ then magnifying power this instrument when image is formed at infinity is ( near point for normal eye$=\mathrm{D}=25 \mathrm{cm}$)

An object is at distance $30 \mathrm{cm}$ from compound microscope of focal length $5 \mathrm{cm}$ and $25 \mathrm{cm}$ for objective and eye piece respectively. Magnifying power of microscope when image is formed at near point is 

A certain far-sighted person cannot see objects closer to the eye than$100 \mathrm{cm}$. The power of lens which will enable him to read at a distance of $25 \mathrm{cm}$ will be 

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

A person can focus objects only when they lie between $0.5 \mathrm{m}$ and $3 \mathrm{m}$ from his eyes. What spectacles should he use to increase his maximum distance of distinct vision to infinity.

A star subtends an angle of $2°$ at eye when seen through the telescope. It subtends an angle of $40°$ at eye. The magnifying power of the telescope is?

A presbyopic patient can see objects only when they lie between $50 \mathrm{cm}$ and $200 \mathrm{cm}$ from the eye. Then the focal length of the correcting lens required while reading is 

A myopic patient uses

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

An object is placed at a distance $u$ from a simple microscope of focal length $f$. The angular magnification obtained depends