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

Which substance is used as a gaseous insulator in high-voltage generators?

$A$ ray of light is incident on an equilateral glass prism placed on a horizontal table. For minimum deviation,which of the following is true?

Where is the International Rice Research Institute $(IRRI)$ located?

The angle of elevation of an object on a hill is observed from a certain point in the horizontal plane through its base to be $30^{\circ}$. After walking $120 \ m$ towards it on level ground,the angle of elevation is found to be $60^{\circ}$. The height of the object (in metres) is:

With increasing principal quantum number,the energy difference between adjacent energy levels in $H$ atom