Two polarisers $P_1$ and $P_2$ are placed such that the intensity of the transmitted light is zero. $A$ third polariser $P_3$ is inserted between $P_1$ and $P_2$. If the transmitted intensity of the light passing through all three polarisers is maximum,what is the angle between the polarisers $P_2$ and $P_3$?

$A$ beam of light $AO$ is incident on a glass slab $(\mu = 1.54)$ in a direction as shown in the diagram. The reflected ray $OB$ is passed through a polaroid. On viewing through the polaroid,we find that on rotating the polaroid: (Given $\tan 57^{\circ} = 1.54$)

$A$ calcite crystal is placed over a dot on a piece of paper and rotated. On seeing through the calcite,one will see:

When a plane-polarised light is passed through an analyser and the analyser is rotated through $90^{\circ}$,the intensity of the emerging light

$A$ beam of unpolarised light of intensity $I_0$ is passed through a polaroid $A$ and then through another polaroid $B$ which is oriented so that its principal plane makes an angle of $45^{\circ}$ relative to that of $A$. The intensity of emergent light is:

An unpolarized light of intensity $I_0$ passes through a polarizer, then through a certain optically active solution, and finally through an analyzer. If the angle between the analyzer and the polarizer is $0^{\circ}$ and the intensity of light emerging from the analyzer is $\frac{3}{8} I_0$, the angle of rotation of the light by the solution with respect to the analyzer is . . . . . . degrees.