What is the function of Copper-$T$?

$\int \frac{3^x dx}{\sqrt{9^x-1}}$ is equal to

$A$ thin prism $P_1$ with angle $4^o$ and made from glass of refractive index $1.54$ is combined with another prism $P_2$ made from glass of refractive index $1.72$ to produce dispersion without deviation. The angle of prism $P_2$ is......$^o$

The correct formula of diammine dichlorodicyanochromate$(III)$ ion is

Two particles $A$ and $B$ initially at rest move towards each other under a mutual force of attraction. At the instant when the speed of $A$ is $v$ and the speed of $B$ is $2v$,the speed of the centre of mass of the system is

Which of the following pairs is correctly matched?