Longitudinal waves involve compressions and rarefactions in the medium, so they are called compressional waves.

Rope waves, spring (coil) waves, and water waves all involve material oscillations, so all listed are mechanical waves.

Period T ∝ √L, so doubling length multiplies period by √2 ≈ 1.414, i.e., ≈1.4 T.

Davisson and Germer's experiment required a nickel crystal target, an electron gun, and a detector, so 'All of these' correctly lists the apparatus used.

Typical wavelengths of light are orders of magnitude smaller than wavelengths of audible sound, so the statement claiming light's wavelength is longer is incorrect.

In standing waves energy oscillates between potential and kinetic forms locally, with no net transport of energy on average.

The period of a simple pendulum is independent of the mass and depends only on length and gravity (T = 2π√(L/g)).

T ∝ √m so if mass becomes 4m, T becomes √4 = 2 times (doubled).

For SHM a = ω²x, so ω² = a/x = 2.0/0.02 = 100, giving ω = 10 rad/s.

Time between successive crests is the period T = 0.2 s, so frequency f = 1/T = 5 Hz.