For a telescope,the focal length of the objective lens is $15\, cm$ and the focal length of the eyepiece is $10\, mm$. If the tube length is $16\, cm$,find the magnification.

If a telescope is reversed,i.e.,viewed from the objective side,what happens to the appearance of the object?

Consider a refracting telescope whose objective has a focal length of $1 \ m$ and the eyepiece has a focal length of $1 \ cm$. The magnifying power of this telescope will be . . . . . . .

$A$ Galileo telescope has an objective of focal length $100 \, cm$ and magnifying power $50$. The distance between the two lenses in normal adjustment will be....$cm$

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

$A$ telescope has an objective lens of focal length $150\,cm$ and an eyepiece of focal length $5\,cm$. If a $50\,m$ tall tower at a distance of $1\,km$ is observed through this telescope in normal setting,the angle formed by the image of the tower is $\theta$,then $\theta$ is close to.....$^o$