The activity of a freshly prepared radioactive sample is 10^{10} disintegrations per second, whose mean life is 10^{9} s. The mass of an atom of this radioisotope is 10^{$$-$$25} kg. The mass (in mg) of the radioactive sample is _________.

A silver sphere of radius 1 cm and work function 4.7 eV is suspended from an insulating thread in free-space. It is under continuous illumination of 200 nm wavelength light. As photoelectrons are emitted, the sphere gets charged and acquires a potential. The maximum number of photoelectrons emitted from the spheres is A $$\times$$ 10^{2} (where 1 < A < 10). The value of Z is _____________.

An $$\alpha$$-particle and a proton are accelerated from the rest by a potential difference of 100 V. After this, their de Broglie wavelengths are $$\lambda$$_{$$\alpha$$} and $$\lambda$$_{p}, respectively. The ratio $${{{\lambda _p}} \over {{\lambda _\alpha }}}$$, to the nearest integer, is _____________.