In intrinsic semiconductors at room temperature, number of electrons and holes are

Figure shows three arrangements of electric field lines. In each arrangement, a proton is released from rest at point $$\mathrm{P}$$ and then accelerated through point $$\mathrm{Q}$$ by the electric field. Points $$\mathrm{P}$$ and $$\mathrm{Q}$$ have equal separations in the three arrangements. If $$p_1 p_2$$ and $$p_3$$ are linear momentum of the proton at point $$\mathrm{Q}$$ in the three arrangement respectively, then

A nucleus with mass number 190 initially at rest emits an alpha particle. If the $$\mathrm{Q}$$ value of the reaction is $$4.5 \mathrm{~MeV}$$, the kinetic energy of the alpha particle is

In a container of height $$21 \mathrm{~cm}$$, certain transparent liquid is taken to a height of $$12 \mathrm{~cm}$$. When seen from above, it appears half filled. The refractive index of the liquid is