Physics

Electronic circuits that perform basic logic operations such as AND, OR, NOT are called logic gates. They are the fundamental building blocks of digital circuits.

At constant temperature, according to Boyle's law (PV = constant), volume V is inversely proportional to pressure P. Therefore, plotting V against 1/P yields a straight line, since V = k × (1/P).

Temperature scales like Celsius are based on two fixed points: the melting point of ice (0°C) and the boiling point of water (100°C) at atmospheric pressure. This provides a reproducible standard for measuring temperature.

The small constriction near the bulb in a clinical thermometer prevents the mercury column from contracting immediately after removal from the patient, allowing the temperature reading to be retained for observation.

X-rays are a form of electromagnetic radiation consisting of high-energy photons. They are not electrons or radioisotopes, and their nature is well understood as high-energy photons.

Donor impurities are elements that have more valence electrons than the host semiconductor, typically group V elements in silicon, which donate electrons. Antimony, phosphorus, and arsenic are group V elements and act as donor impurities, while aluminium is a group III element and acts as an acceptor impurity, not a donor.

The mass of a hydrogen atom is approximately 1836 times the mass of an electron because the hydrogen atom consists of one proton and one electron, and the proton's mass is about 1836 times that of the electron. Therefore, the ratio of the weight (mass) of a hydrogen atom to that of an electron is approximately 1836.

Donor impurities donate electrons (n-carriers), while acceptor impurities create holes (p-carriers). Therefore, donor impurities provide n-carriers and acceptor impurities provide p-carriers, respectively.

Photodiodes are employed as fast counters in electronic circuits because their reverse‑biased junctions exhibit extremely short carrier transit times and very low junction capacitance, delivering nanosecond‑or‑sub‑nanosecond response speeds that allow individual light pulses or photon events to be detected and counted at very high rates; when illuminated, a photodiode generates a current proportional to the incident light intensity, which can be fed directly into a pulse‑shaping or digital‑logic counting stage, and although other fast small‑signal diodes such as the 1N4148 (reverse‑recovery time ≈ 4‑8 ns) and ultra‑fast Schottky diodes (picosecond‑scale recovery) are also useful for high‑frequency pulse counting, the inherent optical sensitivity and rapid response of photodiodes make them the preferred semiconductor devices for fast counting applications. Other options like LEDs, photovoltaic cells, and solar cells serve different purposes and are not typically used as fast counters.

Rutherford's atomic model proposed that electrons orbit the nucleus but did not explain the discrete spectral lines observed in atoms. It predicted that atoms would emit continuous spectra due to accelerating electrons, which was later corrected by Bohr's model. Therefore, the postulate in accordance with Rutherford's model is continuous spectra for atoms.