— the value of $B_{e}$, characterizing the radiation energy source of optical radiation in this direction and is equal: $$ B_{e}=\frac{d \Phi_{e}}{d \Omega d S \cos \varphi} $$ where $d \Phi_{e}$ — flux element surface luminous area $d S$ in the solid angle $d \Omega$ in a direction that makes an angle $\varphi$ with the normal to the element $d S$. Unit B. e. in SI — watts per steradian-square meter — W/(sr m²).

— the value $B_{\varphi}$, which characterizes the glow of the light source in a given direction. B. element $d S$ surface that glows in either direction determined by the ratio of intensity $d l$ of this element in the direction of spread to the area of the projection element on a plane perpendicular to this direction: $$ B_{\varphi}=\frac{d l}{d S \cos \varphi} $$ where $\varphi$ — the angle between the normal to the element $d S$ and this area. Unit B.

— British unit of length equal to $3\ ft = 36\ inches = 0.9144\ m$.

— see. Atomic nucleus.

— the forces acting between nucleons in atomic nuclei and determine (with electromagnetic forces) the structure and properties of nuclei. N.f. are exchange character; it is assumed that the interaction between nucleons carried by sharing pi —mezonamy; N.f. with. — short-force, their range $r_{\mathcal{я}} \sim 10^{-15}$m; they are characterized by the charge independence; N.f. depending on the relative orientation of the spins of the nucleons; N.f.

— the transformation of atomic nuclei, due to the interaction of elementary particles or to each other. N.r. usually carried out by bombarding heavy nuclei easier target particles (nuclei). Among N.r.

— a device for the implementation and support of a controlled nuclear chain reaction separation of heavy nuclei free neutrons.

— resonance absorption energy of an alternating electromagnetic field frequency range substance that is in a constant magnetic field, caused by the magnetism of atomic nuclei. N.m.r. is used to measure the magnetic moments of nuclei, the study and analysis of the structure of matter.

— extremely rapid release of large amounts of energy as a result of nuclear chain reaction or fusion reactions. Acting factors of N.e.: shock wave, light radiation and penetrating radiation.

— a substance that can be used in a nuclear reactor to make a chain reaction of nuclear fission of heavy nuclei. N.f.for n.r. containing nuclear flammable and substance interaction of nuclei with neutrons which leads to the formation of secondary nuclear fuel.