Physics 2023 Jamb Examination

Night vision goggles primarily work by detecting infrared radiation. All objects with a temperature above absolute zero emit thermal radiation in the infrared spectrum. Night vision devices either amplify low levels of ambient visible light or, in the case of thermal imaging, detect the heat signatures (infrared) emitted by living beings and machinery. This allows for clear observation in total darkness where visible light is absent.

A mechanical wave requires a material medium (solid, liquid, or gas) to travel. A longitudinal wave is one in which the particles of the medium vibrate parallel to the direction of energy transport. Sound waves are the classic example; they cannot travel through a vacuum (making them mechanical) and they consist of a series of compressions and rarefactions in the air (making them longitudinal). While water waves are mechanical, they are primarily transverse or circular; light waves are electromagnetic (non-mechanical).

In a series RLC circuit, impedance (\(Z\)) is given by the formula:\[Z = \sqrt{R^2 + (X_L - X_C)^2}\] Resonance occurs when the inductive reactance (\(X_L\)) equals the capacitive reactance (\(X_C\)). At this point, the term \((X_L - X_C)\) becomes zero, and the impedance reduces to its minimum possible value, which is simply the resistance (\(R\)). Because the impedance is at its minimum, the current in the circuit reaches its maximum value.

This question is slightly paradoxical because, by definition, pitch is dictated by frequency. If two notes have the identical frequency, they technically have the same pitch. However, instruments playing the same note are distinguished by their quality or timbre. Timbre is determined by the overtones and harmonics produced, which are heavily influenced by the shape, size, and material of the instrument. In the context of standard physics exams, if the frequency is fixed, the 'pitch' perceived might be slightly colored by these harmonic profiles, though 'timbre' is the more accurate term for the difference.

This is the process of charging by induction.
1. When a negatively charged rod is brought near the neutral sphere, electrons in the sphere are repelled to the far side, leaving the side near the rod positively charged (polarisation).
2. When the sphere is earthed (while the rod is still present), the repelled electrons flow to the ground.
3. If the earth connection is broken and then the rod is removed, the sphere is left with a deficiency of electrons, resulting in a net positive charge. Note: If the rod were taken away *before* removing the earth, the electrons would flow back from the ground and the sphere would remain neutral.