$A$ photon and an electron have equal energy $E$. The ratio $\lambda_{\text{photon}} / \lambda_{\text{electron}}$ is proportional to:

The $IUPAC$ name of $(CH_3)_2CH-CH_2-CH_2Br$ is

The origin is translated to $(1,2)$. The point $(7,5)$ in the old system undergoes the following transformations successively.
$I$. Moves to the new point under the given translation of origin.
$II$. Translated through $2$ units along the negative direction of the new $X$-axis.
$III$. Rotated through an angle $\frac{\pi}{4}$ about the origin of the new system in the clockwise direction. The final position of the point $(7,5)$ is

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

$A$ piece of copper and another of germanium are cooled from room temperature to $80\, K$. The resistance of :

At $T(K)$,$100 \ L$ of dry oxygen is present in a sealed container. It is subjected to silent electric discharge,till the volumes of oxygen and ozone become equal. What is the volume (in litres) of ozone formed at $T(K)$?