Basic Physics

• Stokes' Law Settling Velocity:

• Physical Relationships:
• Sedimentation velocity is directly proportional to the square of particle radius ($r^2$), gravitational acceleration ($g$), and density contrast ($(\rho_s - \rho_l)$).
• Sedimentation velocity is inversely proportional to the dynamic viscosity ($\eta$) of the suspending liquid medium. (Correct answer: Option 4)

• Assertion (A) is False: Rayleigh scattering occurs when particle diameter is much smaller than radiation wavelength ($d \ll \lambda$); its scattering intensity is inversely proportional to the fourth power of wavelength ($I \propto \lambda^{-4}$), NOT the third power.
• Reason (R) is True: Because scattering varies as $\lambda^{-4}$, shorter wavelengths (blue light, $\approx 0.4\ \mu\text{m}$) are scattered far more strongly than longer wavelengths (red light, $\approx 0.7\ \mu\text{m}$), explaining the blue color of the clear daytime sky.
• Conclusion: (A) is false but (R) is true (Option 4).

Correct option: (4) (A) is false but (R) is true.

• Statement (I) is True: Both Electron Paramagnetic Resonance (EPR / ESR) and Nuclear Magnetic Resonance (NMR) spectroscopy exploit the interaction between electromagnetic radiation and magnetic moments oriented in external magnetic fields.
• Statement (II) is False: In EPR, magnetic moments arise from unpaired electron spins (electronic magnetic dipole moments), whereas in NMR, the magnetic moments originate from atomic nuclei possessing non-zero nuclear spin ($I \gt 0$).
• Conclusion: Statement (I) is true but Statement (II) is false (Option 1).

Correct option: (1) Statement (|) is true but Statement (Il) is false