Wave speed on a string v ∝ √(T/μ) and μ ∝ area; doubling T and halving area gives v' = 2v, and since frequency ∝ v for fixed length and mode, frequency doubles.

Huygens' principle cannot account for polarization phenomena, which require transverse wave considerations.

A Polaroid is a polarizing filter used to analyze or produce polarized light.

Distance covered per second is speed; for waves this is wave speed, so option D is correct.

Total energy in SHM is (1/2)kA^2, so it is proportional to the square of the amplitude.

T ∝ 1/√g, so T' = T/√1.02 ≈ 0.99 T.

Increasing tension increases wave speed on the string and thus raises the vibration frequency, as indicated by the OCR mark.

Frequency f = 1/T = 1/0.28 ≈ 3.571 Hz, approximately 3.6 Hz.

The fixed ends are points of zero displacement in standing waves and are therefore nodes, as indicated by the OCR mark.

At resonance the system oscillates with maximum amplitude for the driving frequency matching the natural frequency.