Polarisation

Let's examine each statement about polar molecules to identify the false one:

(A) Centers of positive and negative charges are separated in the absence of external electric field. This is true. Polar molecules have a permanent dipole moment due to differences in electronegativity between the atoms. This means the centers of positive and negative charges are inherently separated even without an external field.

(B) Centers of positive and negative charges are separated in the presence of external electric field. This is true. An external electric field will further polarize the molecule, increasing the charge separation. Even nonpolar molecules experience some charge separation in an external field (induced dipole).

(C) Do not possess permanent dipole moments. This is false. This statement is the opposite of the definition of a polar molecule. Polar molecules, by definition, do possess permanent dipole moments.

(D) Ionic molecule HCl is the example of polar molecule. This is true. HCl is a classic example of a polar molecule due to the significant electronegativity difference between hydrogen and chlorine. Though often confused, ionic bonds have much larger electronegativity differences than polar bonds.

The correct answer is (C) Do not possess permanent dipole moments.

Given:
Initial intensity of unpolarised light =
Intensity after second polaroid =

Step-by-Step Explanation:

Step 1: After passing through the first polaroid

The intensity of unpolarized light after passing through the first polaroid becomes exactly half:

Step 2: After passing through the second polaroid (Malus' Law)

According to Malus' law, the intensity after passing through the second polaroid is given by:

where is the angle between the pass axes of the two polaroids.

Substitute given values clearly:

Simplify to clearly find the angle :

Thus, clearly:

Final Conclusion:
The angle between the pass axes of the polaroids is clearly 45°.