Chemically,borax is ...

At room temperature,a $P-$ type semiconductor has

$A$ uniform meter scale is balanced at the $30 \ cm$ mark on a knife edge,when weights of $60 \ N$ and $10 \ N$ are suspended at the $10 \ cm$ and $80 \ cm$ marks,respectively. The mass of the meter scale is: (in $kg$)

The figure given below shows a small part of human lung where exchange of gases takes place. In which one of the options given below,the one part $A, B, C$ or $D$ is correctly identified along with its function?

Tetrahalides of group $14$ elements (except that of carbon) act as

Explain why $BeH_{2}$ molecule has a zero dipole moment although the $Be-H$ bonds are polar.