When open pipe is closed from one end then second overtone of closed pipe is higher in frequency by 100 Hz than first overtone of open pipe. The fundamental frequency of open end pipe will be (Neglect end correction)

For a uniformly charged plane sheet, the variation of electric field (E) with distance (d) is correctly shown graphically in graph

A point charge 'Q' is placed at the centre of the line joining two equal charges '+q' and '+q'. The value of 'Q' when the system is in equilibrium is

Capacitors of capacities $C_1$ and $C_2$ are connected in series. If the combination is connected to a supply of V volt then the potential difference across capacitor $C_2$ is