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Videos de Conceptos Relacionados

Momentum And Radiation Pressure01:20

Momentum And Radiation Pressure

An object absorbing an electromagnetic wave would experience a force in the direction of propagation of the wave. This force occurs because electromagnetic waves contain and transport momentum. The force accounts for the wave's radiation pressure exerted on the object. Maxwell's prediction was confirmed in 1903 by Nichols and Hull by precisely measuring radiation pressures with a torsion balance. The measuring instrument had mirrors suspended from a fiber kept inside a glass container. Nichols...
Diamagnetic Shielding of Nuclei: Local Diamagnetic Current01:14

Diamagnetic Shielding of Nuclei: Local Diamagnetic Current

An applied magnetic field causes the electrons present in the molecule to circulate, setting up a local diamagnetic current within the molecule. The local diamagnetic current arising from circulating sigma-bonding electrons induces a magnetic field, Blocal that opposes the applied magnetic field, B0. The effective magnetic field experienced by these nuclei is given by the difference between the applied and local magnetic fields in a phenomenon called local diamagnetic shielding. Essentially,...
Atomic Nuclei: Nuclear Spin State Population Distribution01:14

Atomic Nuclei: Nuclear Spin State Population Distribution

Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
Atomic Nuclei: Larmor Precession Frequency01:11

Atomic Nuclei: Larmor Precession Frequency

The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) that causes the mass to 'wobble' around the gravitational field axis in a phenomenon called precession. Similarly, the magnetic moment (μ) of a spinning nucleus precesses due to an external magnetic field directed along the z-axis. The precession of the magnetic moment vector about the magnetic field is called Larmor precession, and the angular frequency...
Atomic Nuclei: Nuclear Magnetic Moment00:59

Atomic Nuclei: Nuclear Magnetic Moment

All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, these nuclei generate a magnetic field (B). This, in turn, gives rise to a magnetic moment (μ), which is randomly oriented in the absence of an external magnetic field. When an external magnetic field (B0) is applied, the magnetic moment vectors can align with the field or against it in 2 + 1 orientations. A hydrogen nucleus, which is just a...
Atomic Nuclei: Nuclear Spin State Overview01:03

Atomic Nuclei: Nuclear Spin State Overview

NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of one, the...

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Video Experimental Relacionado

Updated: Jul 12, 2026

Scattering And Absorption of Light in Planetary Regoliths
11:34

Scattering And Absorption of Light in Planetary Regoliths

Published on: July 1, 2019

Visibilidad de los núcleos de los cometas.

E P Ney

    Science (New York, N.Y.)
    |January 22, 1982
    PubMed
    Resumen

    Obtención de imágenes del cometa Halley.

    Área de la Ciencia:

    • La astronomía y la astrofísica.
    • Ciencia de la ciencia de los cometas.

    Sus antecedentes:

    • La obtención de imágenes de núcleos de cometas es crucial para las misiones espaciales.
    • Las nubes de polvo que rodean a los cometas pueden oscurecer las superficies nucleares.
    • Comprender la densidad del polvo es clave para una observación exitosa.

    Objetivo del estudio:

    • Para evaluar la visibilidad de los núcleos cometarios.
    • Para determinar si el núcleo del cometa Halley puede ser fotografiado.
    • Para evaluar los efectos de oscurecimiento del polvo en las imágenes cometarias.

    Principales métodos:

    • Análisis de datos de fotometría de banda ancha de nueve cometas.
    • Comparación del brillo visual de los cometas observados con el de Halley en 1910.

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  • Evaluación de la densidad del polvo y su impacto en las imágenes.

    • Principales resultados:

    • Las nubes de polvo cometario rara vez interfieren con las imágenes nucleares.
    • El núcleo del cometa West estaba oscurecido por el polvo cerca del perihelio.
    • Es poco probable que el núcleo de Halley esté significativamente oscurecido por el polvo.

    Conclusiones:

    • La obtención exitosa de imágenes del núcleo del cometa Halley es factible.
    • La oscurecimiento del polvo no es una barrera significativa para las observaciones de Halley.
    • Las futuras misiones espaciales pueden continuar con la fotografía nuclear.