When radiation of wavelength $$\lambda $$ is used to illuminate a metallic surface, the stopping potential is V. When the same surface is illuminated with radiation of wavelength 3$$\lambda $$, the stopping potential is $${V \over 4}$$. If the threshold wavelength for the metallic surface is n$$\lambda $$ then value of n will be __________.

A circular coil of radius 10 cm is placed in a uniform magnetic field of 3.0 $$ \times $$ 10^–5 T with its plane perpendicular to the field initially. It is rotated at constant angular speed about an axis along the diameter of coil and perpendicular to magnetic field so that it undergoes half of rotation in 0.2 s. The maximum value of EMF induced (in $$\mu $$V) in the coil will be close to the integer _______.

A 5 $$\mu $$F capacitor is charged fully by a 220 V supply. It is then disconnected from the supply and is connected in series to another uncharged 2.5 $$\mu $$F capacitor. If the energy change during the charge redistribution is $${X \over {100}}J$$ then value of X to the nearest integer is _____.