Which system has maximum entropy? A. Perfect crystal at 0 K B. Completely random system C. Ideal gas at absolute zero D. Vacuum Explanation: Maximum disorder corresponds to maximum entropy.
Which thermodynamic law introduces entropy? A. First law B. Second law C. Third law D. Zeroth law Explanation: Second law defines entropy and direction of processes.
Which particle has zero rest mass? A. Electron B. Proton C. Photon D. Neutron Explanation: Photons are massless.
The fine-structure constant characterizes: A. Gravity strength B. Electromagnetic interaction strength C. Weak force D. Strong force Explanation: It is a dimensionless constant for EM coupling.
Which equation governs quantum evolution? A. Newton’s second law B. Schrödinger equation C. Maxwell equation D. Navier-Stokes equation Explanation: Schrödinger equation describes time evolution of wavefunction.
The Doppler effect for light leads to redshift when: A. Source approaches observer B. Source moves away C. Observer moves toward source D. Wavelength decreases Explanation: Receding source increases wavelength (redshift).
In thermodynamics, enthalpy is defined as: A. (U - PV) B. (U + PV) C. (PV - U) D. (TS) Explanation: Enthalpy is internal energy plus pressure-volume term.
A black hole’s event horizon radius is proportional to: A. Charge only B. Mass C. Temperature D. Spin only Explanation: Schwarzschild radius depends directly on mass.
Which quantity remains invariant under Lorentz transformations? A. Velocity B. Time C. Spacetime interval D. Length Explanation: The spacetime interval is invariant in all inertial frames.
In quantum field theory, virtual particles arise due to: A. Violation of conservation laws B. Heisenberg uncertainty principle C. Thermal fluctuations only D. Classical mechanics Explanation: Energy-time uncertainty allows temporary particle-antiparticle fluctuations.