A sample of a liquid is kept at 1 atm. It is compressed to 5 atm which leads to a change of volume of 0.8 cm³. If the bulk modulus of the liquid is 2 GPa, the initial volume of the liquid was _______ litre.

(Take 1 atm = 10⁵ Pa)

Space between the plates of a parallel plate capacitor of plate area 4 cm² and separation of 1.77 mm, is filled with uniform dielectric materials with dielectric constants (3 and 5) as shown in figure. Another capacitor of capacitance 7.5 pF is connected in parallel with it. The effective capacitance of this combination is _ pF.

(Given $ \epsilon_0 = 8.85 \times 10^{-12} $ F/m)

An electron is released from rest near an infinite non-conducting sheet of uniform charge density '$-\sigma$'. The rate of change of de-Broglie wave length associated with the electron varies inversely as n^th power of time. The numerical value of n is _____.