For a normal eye,the cornea of the eye provides a converging power of $40 \ D$ and the least converging power of the eye lens behind the cornea is $20 \ D$. Using this information,the distance between the retina and the cornea-eye lens can be estimated to be.......... $cm$.

During the electrolytic reduction of alumina,the reaction at cathode is

$A$ car $P$ approaching a crossing at a speed of $10 \, m/s$ sounds a horn of frequency $700 \, Hz$ when $40 \, m$ in front of the crossing. The speed of sound in air is $340 \, m/s$. Another car $Q$ is at rest on a road which is perpendicular to the road on which car $P$ is reaching the crossing. The driver of car $Q$ hears the sound of the horn of car $P$ when he is $30 \, m$ in front of the crossing. The apparent frequency heard by the driver of car $Q$ is ...... $Hz$.

Diazo-coupling is useful to prepare some

A block is sliding down on an inclined plane of slope $\theta$ and at an instant $t = 0$ this block is given an upward momentum so that it starts moving up on the inclined surface with velocity $u$. The distance $(S)$ travelled by the block before its velocity become zero, is . . . . . . . . . . .
($g =$ gravitational acceleration)

In which of the following is a closed circulatory system found?