$A$ man who cannot see clearly beyond $5 \, m$ wants to see stars clearly. He should use a lens of focal length ....... $m$.

$A$ person cannot see an object clearly if it is placed beyond $100 \, cm$. Find the power of the lens required to see an object clearly at infinity.

$A$ short-sighted person can see distinctly only those objects which lie between $10\, cm$ and $100\, cm$ from him. The power of the spectacle lens required to see a distant object is

$A$ person's near point is $50 \, cm$ and his far point is $3 \, m$. The power of the lenses he requires for $(i)$ reading and $(ii)$ seeing distant stars are:

The least distance of distinct vision for a farsighted person is $1 \ m$. The optical power of the lens of his spectacles,which effectively reduces his least distance of distinct vision $(LDDV)$ to $25 \ cm$,is:

An imaginary line joining the optical centre of the eye lens and the yellow point is called as