Let $$L$$ be the line of intersection of the planes $$2x+3y+z=1$$ and $$x+3y+2z=2.$$ If $$L$$ makes an angle $$\alpha $$ with the positive $$x$$-axis, then cos $$\alpha $$ equals

If $${M_O}$$ is the mass of an oxygen isotope $${}_8{O^{17}}$$ , $${M_p}$$ and $${M_N}$$ are the masses of a proton and neutron respectively, the nuclear binding energy of the isotope is

If in a $$p$$-$$n$$ junction diode, a square input signal of $$10$$ $$V$$ is applied as shown

Then the output signal across $${R_L}$$ will be

Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate ?