At the cathode (negative electrode), reduction occurs: $2H^+ + 2e^- \rightarrow H_2$. So hydrogen is produced.

Total internal reflection occurs when light passes from a denser to a rarer medium at an angle equal to or greater than the critical angle. It is the principle behind optical fibres.

Sublimation is the direct conversion of solid to gas. Examples include dry ice (CO₂) and camphor.

During respiration, plants (like animals) absorb O₂ and release CO₂. This is the reverse of photosynthesis.

Scurvy is caused by deficiency of Vitamin C (ascorbic acid), leading to bleeding gums and weakness.

The cerebellum coordinates voluntary movements and is responsible for balance and posture.

The left ventricle pumps oxygenated blood into the aorta, from which it is distributed to the entire body.

Noble gases (He, Ne, Ar, Kr, Xe, Rn) are in Group 18 and are chemically inert due to complete electron shells.

Methane (CH₄) is the simplest hydrocarbon, containing just one carbon atom.

Magnesium loses electrons to oxygen, so it is oxidised. Oxygen is reduced. This is a redox reaction.

Electric motors work on the principle that a current-carrying conductor placed in a magnetic field experiences a force (Fleming's left-hand rule).

The speed of sound in air at 0°C is approximately 331 m/s. It increases with temperature.

Radiation transfers heat through electromagnetic waves and does not need any medium, unlike conduction and convection.

$g = GM/R^2$. If R doubles, $g$ becomes $GM/(2R)^2 = g/4$. So g becomes one-fourth.

Power $P = VI = 220 \times 0.5 = 110$ W.