For an ideal electrical transformer with turns ratio $n=N_p/N_s$, the secondary load $R_L$ appears at the primary as $n^2{R}_L$, while a source resistance $R_g$ appears at the secondary as $R_g/n^2$. A finite magnetizing inductance $L_m$ contributes a parallel branch $i\omega L_m$ at the primary; its magnitude must greatly exceed the reflected load for the loaded input to be approximately resistive. The corresponding unloaded secondary self-reactance is $\omega L_m/n^2$. That reactance is distinct from the source's transformed output resistance. A specification that simultaneously calls the loaded input matched to a small resistance and calls the primary impedance very large must distinguish these two branches.

A Thévenin equivalent represents a network at two terminals by a voltage source in series with its Thévenin resistance. It reproduces the terminal relation under the assumptions of Thévenin's theorem.

At fixed pressure, the temperature derivative of a reaction or transformation enthalpy is the corresponding difference in heat capacity at constant pressure:Use a consistent molar or mass basis and retain each phase's range of stability when applying the relation. A latent enthalpy evaluated along a pressure-dependent phase coexistence curve can also have a pressure-variation contribution; the fixed-pressure derivative must not automatically be identified with that full derivative.

Radio communication conveys information using radio waves coupled into and out of space by antennas. Amplitude modulation and frequency modulation vary a carrier wave; wireless telegraphy can instead encode symbols in transmission intervals. The useful separation is between the rapid electrical oscillation and the slower message timing. A receiver needs both frequency selection and a way to turn its selected signal into a readable output.

Telegraphy represents written symbols by agreed sequences of distinguishable signals. In wireless telegraphy, a key can select short and long transmission intervals; a receiver must recover their timing, rather than reproduce every rapid electrical oscillation as a visible mark.

The convention used here chooses units in which the numerical values of the reduced Planck constant, electron mass, elementary charge and $4\pi$ times the vacuum permittivity are one.

A Haworth projection depicts cyclic monosaccharide connectivity and substituents above or below a reference ring plane; it does not assert a physically flat ring.

Spectroscopy using X-rays, including X-ray emission spectroscopy.

Spectroscopy based on the energy distribution of electrons, including photoemission spectroscopy.

Assigning wavelengths to detector positions using reference features, so a change in a spectral-line position can be interpreted as a physical wavelength shift.

Comparison of an observed spectrum with a shifted template or line mask as a function of trial Doppler velocity. The fitted correlation centre combines the position information from many spectral lines; its sign convention can produce a peak or a dip.

Energy resolution specifies the characteristic energy separation or broadening that an instrument can distinguish, with a stated width convention and measurement geometry. Resolving a phonon in inelastic scattering requires measuring a small energy transfer as well as momentum transfer. It is distinct from the incident beam's central energy.

Inverse photoemission spectroscopy injects an electron of known kinetic energy into a sample and detects the photon emitted as it enters an unoccupied electronic state. Conservation of energy, together with incident-angle information and an appropriate surface model, probes the unoccupied electronic band structure. Ordinary angle-resolved photoemission spectroscopy instead removes electrons from occupied states.