Name: radiation pressure in light and comets
Uploaded: 2023-04-30T12:46:50.000Z
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K12 Standards

Pennsylvania State Academic Standards

9-12

Earth and Space Science

Earth's Systems

3.3.9-12.H

Momentum And Radiation Pressure

Les ondes électromagnétiques transportent l’élan lorsqu’elles voyagent dans l’espace. La densité de quantité de mouvement correspondante est exprimée en fonction de l’amplitude du vecteur de Poynting et de la vitesse de la lumière.
En substituant le volume occupé par l’onde qui traverse une zone dans un court intervalle de temps, on peut obtenir le débit de quantité de mouvement par unité de surface.
Le taux moyen de transfert de quantité de mouvement par unité de surface est obtenu en remplaçant la valeur moyenne du vecteur de Poynting par l’intensité.
En raison du transfert de quantité de mouvement, les ondes électromagnétiques exercent une pression sur la surface, connue sous le nom de pression de rayonnement.
Or, le taux moyen de variation de la quantité de mouvement est égal à la force moyenne et la force par unité de surface est la pression de rayonnement.
Ainsi, la pression de rayonnement est directement proportionnelle à l’intensité de l’onde.
Si la surface absorbe parfaitement l’onde électromagnétique, la quantité de mouvement correspondante est également transférée complètement à la surface.
Pour une surface parfaitement réfléchissante, le changement de quantité de mouvement sera doublé. Ainsi, la pression de rayonnement double également.

<ol>
	<li>OpenStax. (2019). Physique universitaire Vol. 2. [Version Web]. Extrait de <a href="https://openstax.org/books/university-physics-volume-2/pages/16-4-momentum-and-radiation-pressure">16.4 Quantité de mouvement et pression de rayonnement - Physique universitaire Volume 2 | OpenStax</a></li>
</ol>

momentum et pression de radiation

Un objet qui absorbe une onde électromagnétique subirait une force dans la direction de propagation de l'onde. Cette force se produit parce que les ondes électromagnétiques contiennent et transportent de l'impulsion. La force correspond à la pression de radiation de l'onde exercée sur l'objet. La prédiction de Maxwell a été confirmée en 1903 par Nichols et Hull en mesurant précisément les pressions de radiation avec une balance à torsion. L'instrument de mesure comportait des miroirs suspendus à une fibre maintenue à l'intérieur d'un récipient en verre. Nichols et Hull ont obtenu une légère déviation mesurable des miroirs en éclairant l'un d'entre eux. À partir de la déviation mesurée, ils ont calculé la force non équilibrée sur le miroir et ont obtenu un accord avec la valeur prédite de la force. La pression de radiation exercée par une onde électromagnétique sur une surface parfaitement absorbante s'avère être égale à la densité d'énergie de l'onde. Supposons que le matériau soit parfaitement réfléchissant et que les ondes électromagnétiques soient incidentes perpendiculairement à la surface. Dans ce cas, la pression exercée est deux fois plus grande car la direction de l'impulsion s'inverse lors de la réflexion.

La pression de radiation joue un rôle dans l'explication de nombreux phénomènes astronomiques observés, y compris l'apparence des comètes. Lorsqu'une comète s'approche du Soleil, elle se réchauffe et sa surface, composée de gaz gelés et de particules de roche et de poussière, s'évapore. La comète possède une coma, une zone floue autour d'elle constituée de gaz et de poussière. Certains des gaz et de la poussière forment des queues lorsqu'ils quittent la comète. La queue ionique est principalement composée de gaz ionisés. Ces ions interagissent électromagnétiquement avec le vent solaire, un flux continu de particules chargées émis par le Soleil. La force du vent solaire sur les gaz ionisés est suffisamment forte pour que la queue ionique pointe presque toujours directement loin du Soleil. La deuxième queue est composée de particules de poussière. Étant donné que la queue de poussière est électriquement neutre, elle n'interagit pas avec le vent solaire. Cependant, cette queue est affectée par la pression de radiation produite par la lumière du Soleil. Bien que relativement faible, cette pression est suffisamment forte pour que la queue de poussière soit déplacée de la trajectoire de la comète.

Momentum et pression de radiation

Un objet absorbant une onde électromagnétique subirait une force dans la direction de propagation de l’onde. Cette force se produit parce que...

Education

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Unit 1

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Electromagnetic Waves

Ondes électromagnétiques

KEY TERMS AND CONCEPTS

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radiation pressure in light and comets

Radiation pressure is the force that electromagnetic waves can exert on matter. It appears because light carries momentum, so an object that absorbs a wave feels a push in the direction the wave travels. This same force helps explain why sunlight can affect small particles in space.

Maxwell predicted radiation pressure, and Nichols and Hull confirmed it in 1903. They used a torsion balance with mirrors suspended from a fiber inside a glass container. When they shone light on one mirror, the mirrors shifted slightly. From that tiny deflection, they calculated the unbalanced force and found agreement with the predicted value.

The size of the pressure depends on the surface. For a perfectly absorbing surface, the radiation pressure equals the energy density of the wave. For a perfectly reflecting surface with the wave hitting straight on, the pressure is twice as large because the light reverses momentum when it reflects.

Radiation pressure also helps explain comet tails. When a comet nears the Sun, it warms up and releases frozen gases, rock, and dust. This forms a coma, which is the hazy cloud around the comet, and it can also create tails.

The ion tail is made mostly of ionized gases. These ions interact with the solar wind, a stream of charged particles from the Sun, and the tail usually points away from the Sun. The dust tail is different. It contains neutral dust, so it does not respond to the solar wind. Instead, sunlight’s radiation pressure pushes the dust tail away from the comet’s path.

Radiation Pressure in Light and Comets

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momentum and radiation pressure

Radiation pressure is the force that electromagnetic waves can exert on matter. It appears because light carries momentum, so an object that absorbs a wave feels a push in the direction the wave travels. This same force helps explain why sunlight can affect small particles in space. Maxwell predicted radiation pressure, and Nichols and Hull confirmed it in 1903. They used a torsion balance with mirrors suspended from a fiber inside a glass container. When they shone light on one mirror, the...

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key terms and concepts

Explore how light carries momentum, creates radiation pressure, and was measured by Nichols and Hull. See how it helps shape comet tails.

Radiation Pressure in Light and Comets | JoVE K12

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JoVE Core Physique présente plusieurs branches de la physique fondamentale grâce à des vidéos animées concises et faciles à comprendre ; cela inclut: la cinématique, la dynamique, la mécanique des fluides, la mécanique statique, les ondes et l'acoustique. En parallèle, les vidéos de scientifiques à l'action démontrent l'application de concepts associés à ces domaines dans des expériences de recherche classiques et originales réalisées dans des laboratoires modernes du monde entier.

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3.3.9-12.E

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Waves and Electromagnetic Radiation

3.2.9-12.V

Louisiana Student Standards for Science

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HS-ESS2-1

HS-ESS2-4

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Waves And Their Applications In Technologies For Information Transfer

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Virginia  Standards of Learning

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PS.7

PS.7.a

Alabama Course of Study Science

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Florida Department of Education

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south-carolina-college-and-career-ready-science-standards

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3.3.9-12.L

Radiation Pressure in Light and Comets

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