Name: electromagnetic wave reflection at conductors
Uploaded: 2023-09-18T17:11:17.000Z
Duration: 1 min 15 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Physical Science

PS.7

PS.7.a

Standing Electromagnetic Waves

きついひもで形成された定在波を思い出してください。 
定在波は、反対方向に移動するが、振幅と周波数が同じ2つの波の組み合わせです。
y-z平面に配置された完全な導電シートを考えてみましょう。直線偏光電磁波は、負のx方向に移動しながらシートに当たります。
入射波は導体の表面に電流を誘導し、その結果、追加の電界が発生し、入射波と同じ周波数と振幅の反射波が生成されます。
これら2つの波の重ね合わせにより、定在波が生成されます。これらの式を単純化すると、電界と磁場の大きさがゼロになる波上の点が得られます。これらはノードまたはノード平面と呼ばれます。
アンチノードは、振幅が最大正の変位から最大の負の変位になる点です。
電場のノードは磁場の反ノードと一致し、その逆も同様です。したがって、各ポイントで位相が90度ずれています。

<ol>
	<li>ヤング、H.D.およびフリードマン、RA(2012)。現代物理学と大学物理学。カリフォルニア州サンフランシスコ:ピアソン。セクション32.5;1069〜1070ページ。</li>
</ol>

定在電磁波

電磁波は反射する可能性があります。 導体または誘電体の表面は反射体として機能します。 電場と磁場は重ね合わせ原理に従いますが、電磁波も重ね合わせ原理に従います。 入射波と反射電磁波が重なると、張られた紐に生じる定在波に似た定在波が生じます。

完全導体のシートが yz 面に置かれ、 負の x 方向に進む直線偏波の電磁波がそれに当たるとします。 電場は完全な導体の表面に平行な成分を持つことができないため、 電場はyz面のどこでもゼロでなければなりません。 入射電磁波の電場はyz面では常にゼロではありませんが、この入射波は導体の表面に振動電流を誘導し、追加の電場を引き起こします。 。 この電界と入射電界の合力である正味の電界は、導体の内部および表面上のどこでもゼロになります。 導体の表面に誘導された電流は、平面から外へ伝わる反射波も生成します。 重ね合わせの原理は、磁場と同様に、任意の点における総磁場は入射波と反射波の電場の合力であると述べています。 入射波と反射波が重なると定在波が生成されます。

<img alt="Equation1" src="/files/ftp_upload/13829/13829_Equation_1.png" style="text-align: center; height: 24px;" />

<img alt="Equation2" src="/files/ftp_upload/13829/13829_Equation_2.png" style="text-align: center; height: 22px;" />

これらの式を単純化すると、電場と磁場の大きさがゼロになる波上の点が得られます。 これらはノードまたはノード面と呼ばれます。 隣接する 2 つの節面の中間には、最大振幅の面があります。 これらは節腹面です。

全電界はサイン関数であり、全磁界はコサイン関数です。 したがって、2 つの場の正弦波変化は各点で位相が異なります。 電場の節は磁場の腹と一致し、その逆も同様です。 したがって、それらは 90° になります。 各点で位相がずれています。 これは、電界と磁界の正弦波変化が特定の点で同位相となる、一方向に進む波とは対照的です。

電磁波を反射することができます。導体または誘電体の表面は、反射板として機能することができます。電場と磁場が従うと...

Education

JoVE Core

Physics

物理学

Unit 1

ユニット1

Electromagnetic Waves

電磁波

KEY TERMS AND CONCEPTS

主要用語と概念

electromagnetic wave reflection at conductors

Electromagnetic waves can reflect from a conductor or a dielectric. When the reflected wave combines with the incoming wave, the result is a standing electromagnetic wave. This is similar to the standing waves formed on a stretched string.

To see how this happens, consider a perfect conductor placed in the yz-plane. A linearly polarized electromagnetic wave moving in the negative x-direction strikes the surface. The electric field cannot have a component parallel to the surface of a perfect conductor, so the electric field must be zero everywhere in the yz-plane.

The incident wave is not zero at the surface, but it induces oscillating currents on the conductor. These currents create an additional electric field. The net electric field is the vector sum of the incident and induced fields, and it is zero everywhere inside and on the conductor's surface. The same surface currents also produce a reflected wave that moves away from the plane.

The total field at any point is the vector sum of the incident and reflected electric fields, and the same idea applies to the magnetic field. This superposition creates standing waves. The places where the electric or magnetic field magnitude is zero are called nodes, or nodal planes. The planes halfway between adjacent nodes have maximum amplitude and are called antinodal planes.

For these standing waves, the total electric field follows a sine function, while the total magnetic field follows a cosine function. The two fields are therefore 90° out of phase at each point. Electric field nodes line up with magnetic field antinodes, and magnetic field nodes line up with electric field antinodes. This is different from a wave traveling in one direction, where the electric and magnetic fields are in phase at a given point.

Electromagnetic Wave Reflection at Conductors

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key terms and concepts

Explore how reflected electromagnetic waves form standing patterns at conductors, with nodes, antinodes, and electric and magnetic fields out of phase.

Electromagnetic Wave Reflection at Conductors | JoVE K12

physics

JoVE Core 物理学は、運動学、力学、流体力学、静力学、波動、音響などの基礎的な物理学の理論と応用を、簡潔でわかりやすいアニメーション ビデオで紹介します。さらに、科学者の実際のビデオでは、世界中の今日の研究所で行われている古典的および独自の研究実験における関連概念の適用を示しています。

Minnesota Academic Standards in Science

9-12

4.2.1 9P.3.2.2.1

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

High School

waves-and-their-applications-in-technologies-for-information-transfer

Waves and Their Applications in Technologies for Information Transfer

HS-PS4-5

Alabama Course of Study Science

9-12.PS.2.2.e

9-12.P.3.7.c

Florida Department of Education

SC.912.P.10

SC.912.P.10.17

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

South Carolina College and Career Ready Science Standards

P-PS4-2

P-PS4-4

Earth and Space Science (ESS)

Earth’s Place in the Universe

E-ESS1-2.

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PS.7.b

Electromagnetic Wave Reflection at Conductors

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