Three charges $Q,-2 q$ and $-2 q$ are placed at the vertices of an isosceles right-angled triangle as shown in figure. The net electrostatic potential energy is zero if $Q$ is equal to
A spring has length ' $L$ ' and force constant ' $K$ '. It is cut into two springs of length ' $\mathrm{L}_1$ ' and ' $\mathrm{L}_2$ ' such that $\mathrm{L}_1=\mathrm{nL}_2$ ( n is an integer). The force constant of the spring of length ' $\mathrm{L}_2$ ' is
The period of revolution of planet A around the sun is 8 times that of $B$. The distance of $A$ from the sun is how many times greater than that of $B$ from the sun?
In Young's double slit experiment, fringe width is 1.4 mm with light of wavelength $6000 $$\mathop {\rm{A}}\limits^{\rm{o}} $. If the light of wavelength $5400 $$\mathop {\rm{A}}\limits^{\rm{o}} $ is used, with no other change in the experimental set up. The change in fringe width is