Exercise-Choice

Two parallel wires separated by $2 \mathrm{m}$ carry currents of $3\mathrm{A}$ each in the opposite directions. Find the magnetic induction for the points between the wires at a distance $50 \mathrm{cm}$from each wire.

State Gauss’ law for magnetism. Explain its significance.

When can a charge act as a source of electromagnetic wave?

What is meant by critical angle for a given refracting medium? Establish a relationship between critical angle and refractive index. What is a total internal reflection, and when does it take place?

Find De-Broglie wavelength of $150 \mathrm{eV}$ electron.

State Bohr’s postulate to define stable orbits in hydrogen atom. How does de Broglie’s hypothesis explain the stability of these orbits ?

Twelve resistors each of resistance $r$ are joined to form a cube as shown in the figure given below. Find the equivalent resistance between the diagonally opposite points $A$ and $F$.

A symmetric biconvex lens of the radius of curvature $R$ and made of glass of refractive index $1.5$, is placed on a layer of liquid placed on top of a plane mirror as shown in the figure. An optical needle with its tip on the principal axis of the lens is moved along the axis until its real, inverted image coincides with the needle itself. The distance of the needle from the lens is measured to be $x$. On removing the liquid layer and repeating the experiment, the distance is found to be $y$. Obtain the expression for the refractive index of the liquid in terms of $x$ and $y$.