Name: electromagnetic modes in a microwave cavity
Uploaded: 2023-09-18T17:11:21.000Z
Duration: 1 min 28 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Physical Science

PS.7

PS.7.a

Standing Waves in a Cavity

Mikrodalga fırınlar, yiyecekleri ısıtmak için elektromanyetik dalgalar kullanır.
Çoğu gıda maddesi, alternatif elektrik alanı ile ileri geri dönen su gibi polar moleküller içerir. Çevirme sırasında moleküller diğer moleküllerle sürtünmeye uğrar, bunun sonucunda ısı üretilir.
Mikrodalga odası, metal yüzeyden yansıma ile duran elektromanyetik dalgaların oluştuğu bir rezonans boşluğu görevi görür. İki metalik yüzey düğüm düzlemlerine yerleştirilir.
Bu nedenle, düzlemler arasındaki mesafe, dalga boyunun yarısının tam katı olmalıdır.
Bu koşulu sağlayan dalga boylarına karakteristik dalga boyları denir ve karşılık gelen frekanslara karakteristik frekanslar denir.
Her karakteristik frekans, dalga şekli ve düğüm modeli bir dizi normal mod oluşturur.
Örneğin, tipik bir ev tipi mikrodalga, su molekülleri tarafından kolayca emilen bir dalga boyuna karşılık gelen 2.4 gigahertz'de çalışır.
Bu dalga boyunun 6.1 santimetre aralıklı düğümleri vardır, bu da yiyeceğin bu noktalarda soğuk olacağı ve antinodlarda maksimuma kadar ısıtılacağı anlamına gelir.
Böylece, mikrodalga fırının döner tablası, düzgün bir ısı dağılımına sahip olacak şekilde döndürülür.

<ol>
	<li>Genç, H.D. ve Freedman, R.A. (2012). Modern Fizik ile Üniversite Fiziği. San Francisco, Kaliforniya: Pearson. Bölüm 32.5; Sayfa 1071.</li>
</ol>

bir hacimde duran dalgalar

Ev mikrodalga fırınları ve lazerler, bir hacimde duran elektromanyetik dalgaların örnekleridir. İki iletken metal levha, düğüm noktalarında paralel olarak yerleştirildiğinde, duran dalgaların oluştuğu bir hacim oluşturur. İki levha arasındaki boşluk, x= 0 ve x= L noktalarında tutulan gerilmiş bir ip gibi benzetilebilir. Burada, iki levha arasındaki mesafe 'L' dalga boyunun yarısının tam sayı katı olmalıdır. Bu koşulu sağlayan dalga boyları aşağıdaki gibi verilir:

<img alt="Equation1" src="/files/ftp_upload/14213/14213_Equation_1.png" style="text-align: center; height: 40px;" />

Karakteristik frekanslar ise aşağıdaki gibidir:

<img alt="Equation2" src="/files/ftp_upload/14213/14213_Equation_2.png" style="text-align: center; height: 40px;" />

Her bir karakteristik frekans, dalga şekli ve düğüm deseni bir dizi normal mod oluşturur. Dalga boyu, düğüm konumlarını ölçerek tahmin edilebilir ve frekans biliniyorsa, dalga hızı da belirlenebilir.

İletken yüzeylerin dışında, elektromanyetik dalgaların yansıması, dielektrik veya manyetik özellikleri farklı iki yalıtkan malzeme arasındaki bir arayüzde de gerçekleşebilir. Mekanik analoji ise eşit gerilime sahip ancak farklı lineer kütlesel yoğunluğa sahip iki ipin birleşimi gibidir. Tipik olarak, böyle bir sınır yüzeyine ışınlanan bir dalga ikinci malzemeye kısmen iletilir ve birinci malzemeye geri yansır. Örneğin, ışık cam bir pencereden geçer, ancak yüzeyleri de ışığı yansıtır.

Bir Hacimde Duran Dalgalar

Ev tipi bir mikrodalga fırın ve lazerler, bir boşlukta duran elektromanyetik dalgalara örnektir. İki iletken metal plaka paralel olarak yerleştirildiğinde...

Education

JoVE Core

Physics

Fizik

Unit 1

Ünite 1

Electromagnetic Waves

Elektromanyetik Dalgalar

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

electromagnetic modes in a microwave cavity

Electromagnetic waves can form standing patterns inside a cavity. Household microwaves and lasers are common examples of this effect. When two conducting metal plates are placed parallel at the nodal planes, they create a space where standing waves can exist.

The cavity between the plates works like a stretched string fixed at x = 0 and x = L. The distance L must be an integer multiple of half a wavelength. The wavelengths that meet this condition have matching frequencies, and each frequency, wave shape, and node pattern is a normal mode.

Node positions can be measured to estimate the wavelength. If the frequency is known, the wave speed can also be found. Electromagnetic waves can also reflect at the boundary between two insulating materials with different dielectric or magnetic properties.

This kind of boundary acts like a junction between two strings with the same tension but different linear mass density. A wave that reaches the boundary is partly transmitted into the second material and partly reflected back. Light passing through a glass window is one example, since the surfaces transmit some light and also reflect some of it.

Electromagnetic Modes in a Microwave Cavity

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Electromagnetic waves can form standing patterns inside a cavity. Household microwaves and lasers are common examples of this effect. When two conducting metal plates are placed parallel at the nodal planes, they create a space where standing waves can exist. The cavity between the plates works like a stretched string fixed at x = 0 and x = L. The distance L must be an integer multiple of half a wavelength. The wavelengths that meet this condition have matching frequencies, and each frequency,...

key terms and concepts

Learn how standing electromagnetic waves form in a cavity, why only certain wavelengths fit, and how reflections create partial transmission at boundaries.

Electromagnetic Modes in a Microwave Cavity | JoVE K12

physics

JoVE Temel Fizik, kinematik, dinamik, akışkanlar mekaniği, statik, dalgalar ve akustik dahil olmak üzere temel fizik konularının teorisini ve uygulamasını kısa ve anlaşılması kolay animasyonlu videolarla tanıtıyor. Ek olarak, sektör içindeki bilim insanı videoları, dünya çapındaki günümüz laboratuvarlarında gerçekleştirilen klasik ve orijinal araştırma deneylerinde ilgili kavramların uygulanmasını göstermektedir.

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PS.7.b

Electromagnetic Modes in a Microwave Cavity

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