What is Cavity: Definition and 273 Discussions

A body cavity is any space or compartment, or potential space in the animal body. Cavities accommodate organs and other structures; cavities as potential spaces contain fluid.
The two largest human body cavities are the ventral body cavity, and the dorsal body cavity. In the dorsal body cavity the brain and spinal cord are located.
The membranes that surround the central nervous system organs (the brain and the spinal cord, in the cranial and spinal cavities are the three meninges. The differently lined spaces contain different types of fluid. In the meninges for example the fluid is cerebrospinal fluid; in the abdominal cavity the fluid contained in the peritoneum is a serous fluid.
In amniotes and some invertebrates the peritoneum lines their largest body cavity called the coelom.

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  1. Domenico94

    Electric field outside of a cavity

    Homework Statement Hi everyone. I m just studying capacitors but I have problems with gauss law. In one exercise it says that we have a sphere(cavity) of radius r, with a charge q placed inside the sphere of it. Wie have to find the electric field inside and outside sphere. The solution says...
  2. L

    Could a cavity magnetron be used for infrared instead

    of microwaves?
  3. C

    Given Ez, with Bz = 0, how to find other components?

    Hey there, I have a quick question, and it can be answered with a reference to a book chapter of article. If I'm given the z component of the electric field inside a resonant cavity, and furthermore, if it's set that Bz = 0, how do I determine the other components for both E and B?
  4. L

    Electric field inside a dielectric sphere with cavity

    Original Problem: "A sphere of radius a is made of a nonconducting material that has a uniform volume charge density [PLAIN]http://jkwiens.com/2007/10/24/answer-electric-field-of-a-nonconducting-sphere-with-a-spherical-cavity/d2606be4e0cd2c9a6179c8f2e3547a85_2.gif. A spherical cavity of...
  5. O

    Volume of a Cavity in an Iron Casting

    Homework Statement An iron casting weighs 300 N in air and 200 N in water. What is the volume of cavities in the casting, if the density of iron is 7800 kg/m3 ? Homework Equations d = m/V Fg = mg The Attempt at a Solution I was not sure in the slightest of how to solve this problem. So I...
  6. H

    Electric field within a conductor with a cavity

    Homework Statement I'm having trouble understanding my book's explanation of the electric field within a conductor with a cavity. http://imgur.com/mjHRQoq Homework Equations EA = qenc/ε The Attempt at a Solution So I understand the first two pictures, the electric field is 0 because the...
  7. D

    Cylindrical cavity resonator problem

    Homework Statement Q. A cylindrical cavity resonator has diameter of 24 mm and length 20 mm. The dominant mode and the lowest frequency band are operated as ? I am providing a picture of problem to show the options given to me. I solved the problem by calculating resonant frequency for cavity...
  8. D

    Waveguides and Cavity resonator Equation confusion

    Homework Statement This is not a homework question and I am asking this question out of curiosity. We have been taught rectangular wave guides and cavity resonator recently and I don't want to gulp the wave equations as it is, so the problem that I am facing ( I have written it on paper and...
  9. D

    Microwave rectangular cavity resonator ?

    Homework Statement I am putting the picture of the equation given to me in book , I feel it to be wrong please tell me that is the equation written in book correct or not ! Homework EquationsThe Attempt at a Solution
  10. F

    Microwave cavity resonators as filters

    I'm not sure if I should be asking this in the EE section, but here goes. I'm trying to understand more about resonant cavities and how they act to filter out frequencies other than the resonant frequency. In the case where a cavity resonator is coupled between two transmission lines, how...
  11. W

    Electric Potential V inside nonconducting sphere with cavity

    Homework Statement A nonconducting sphere of radius r_2 contains a concentric spherical cavity of radius r_1. The material between r_1 and r_2 carries a uniform charge density rho_E(C/m^3). Determine the electric potential V, relative to V=0 at r= infinity, as a function of the distance r from...
  12. C

    Statistical mechanics: Total number of photons in a cavity

    Homework Statement Show that the number of photons in equlibrium at tempertaure t in a cavity of volume V is, N=[2.404 V (t/ħc^3]/Pi^2 The total number of photons is the sum of the average number of photons over all modes n->∑<s> Homework Equations n=Sqrt[nx^2+ny^2+nz^2] ωn=(n Pi c)/L...
  13. W

    Cavity quantum electrodynamics

    hi, i am studing cavity QED - but needs some comprehensive book on that - i will be very grateful if someone guide me in this regard.thanks
  14. @

    Electrostatic shielding in a cavity

    Suppose a constant electric field exists in space as shown in the file and a open lid cube type conductor is brought inside the field. What would be the electric field in the question marked area. Would it be zero or equal to original electric field.
  15. D

    How Does a Laser's Resonant Cavity Create Multiple Wavelengths?

    Homework Statement The fact that a laser's resonant cavity so effectively sharpens the wavelength can lead to the output of several closely spaced laser wavelengths, called longitudinal modes. Here we see how. Suppose the spontaneous emission serving as the seed for stimulated emission is of...
  16. H

    How do electrons induce resonance in a cavity resonator?

    I've been reading lately in particle accelerators and electrons and it got me wondering. How do electrons induce resonance in a cavity resonator? Do they have to first be accelerated to one of the walls of the cavity where they then bounce off toward the other wall?
  17. L

    Calculating Magnetic Field Due to Multiple Cavities Using Ampere's Law

    Homework Statement A long conductive cylinder contains two cylindrical cavities, as shown in the diagram. Find the magnetic field produced at point P just above the surface of the cylinder, the total current in the I and uniform current density over its section. Homework Equations...
  18. C

    Derivation of Planck's law and the shape of the cavity

    When Planck's law is derive a cubical cavity is often used (for example in: http://disciplinas.stoa.usp.br/pluginfile.php/48089/course/section/16461/qsp_chapter10-plank.pdf) However, the result is applied generally. But in general, it seems like the wave lengths of the standing waves will...
  19. kartikwat

    Electric field inside a cavity

    I have read that electric field inside a cavity of irregular conducting surface having any charge is zero.how is this possible?
  20. J

    Wall Cavity Insulation Question?

    Homework Statement Hi guys, I have read this question over and over and have no idea where to start, would anyone be able to help. The Question Up to 20% of all heat lost in domestic dwellings occurs through walls. Many modern Australian homes are built by constructing walls...
  21. L

    Two atoms in an optical cavity.

    Hello,I have a question about 2 (or more) atoms coupled to an optical cavity. The equations of motion in the interaction picture for 2 atoms in resonnance with an optical cavity starting from 1 excited atom (C_{eg,0}(t_0) = 1 ) (g is the coupling constant) \begin{cases} \dot{C}_{eg,0} &= -...
  22. L

    Understanding the Working of Two Cavity Klystrons: An In-Depth Explanation

    I am reading Two cavity Klystrons but not able to understand at all. I have a lot of questions about its working. Q1. Firstly, as we know that Klystrons are used as amplifiers for microwave frequency and conventional vacuum tubes can't be used due to interelectrode capacitance and lead...
  23. G

    B field inside conductor with assymetric cavity

    Homework Statement Infinite straight conductor, parallel with z axis, of radius R1 with a cylindrical cavity of radius R2. The axis of the cavity passes through the point <0,b,0>. A current I flows through the conductor. The current density is homogenous inside the cundoctor. Find the...
  24. D

    Cylindrical resonance cavity problem

    Hello all! Homework Statement Consider a cylindrical cavity with length "d" and radius "a". Find the corresponding electric field, and the dispersion relation therein. Homework Equations Maxwell's equations. The Attempt at a Solution I tried to solve the appropriate vector Helmholtz...
  25. T

    How Long Will It Take for an Electron to Reach the Sphere's Edge?

    Homework Statement A cavity of radius r is present inside a solid dielectric sphere of radius R, having a volume charge density of ρ. The distance between the centers of the sphere and the cavity is a. An electron e is kept inside the cavity at an angle θ = 45° as shown. How long will it...
  26. T

    Neutral conductor has a hollow cavity within it

    Homework Statement a neutral conductor has a hollow cavity within it. When a point charge q = +6.3 nC is placed into this cavity How much charge will be found on each surface of the conductor? inner: -6.3 nC (negative charge being attracted by the positive charge that being put in the...
  27. C

    What software is recommended for designing microwave cavities?

    Hi all, I need a proper software for designing microwave cavities. I intend to use simple base geometries (e.g. closed box) with some modifications, like holes for optical access or for feeding the MW. These modifications however may seriously affect the Q factor, the frequency or might...
  28. A

    Calculating Eigenenergies of Photon in Cavity Hamiltonian

    Hey, in my notes I have calculated the Eigenenergie of the Hamiltonian: H= \hbar \omega (n+\frac{1}{2}) \cdot \begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix} +\hbar \begin{pmatrix} \frac{\Omega_0 -\omega_0}{2} & g \sqrt{n+1} \\ g \sqrt{n+1}& -\frac{\Omega_0...
  29. kmm

    Charge within a cavity inside a conducting material

    Suppose I have a charge inside a conductor as shown in the image I've attached. For any charge distribution: \oint \mathbf{E} \cdot d \mathbf{a} = 0 I can see that if I took some path from the charge, through the conductor, and back to the charge, the integral would be zero still. Now, that...
  30. P

    The quality factor of cavity resonator

    Hello i have to derive the quality factor Q i must start with Q=2\pi\frac{internal-stored-energy}{energy-loss-per-cycle} the quality factor should be in terms of λ so the last equation shall be Q=\frac{4\pi L}{\lambda (1-R)} i searched in google but i always get the Q-factor in...
  31. K

    Measuring size of a body cavity

    I have to measure the size of a cavity of a animal body(s). What is more important I need to measure it on several bodies and compare the results. The cavity is small and contains liquid. That liquid can be extracted and that sets the volume of cavity to 0. It's important to note that the...
  32. Y

    Clocks inside a cavity inside a collapsing dust shell

    Consider a perfectly spherical dust shell with a large internal cavity. Imagine there is a moment when the dust is momentarily stationary and there is a string of clocks strung out along a radial axis. At this instant, I will assume that the spacetime inside the cavity is flat and all the clocks...
  33. C

    How to find Resonance frequency of rectangualr cavity from FDTD data

    Hello, I have written 3D FDTD code with Mur ABC which gives correct results for time domain data. Now I want to compute the resonance frequency of a rectangular cavity using this 3D FDTD code. I don't know how I will do that. Would someone please advise me the steps I need to follow now to...
  34. M

    Charge and field distribution for spherical conductor with cavity

    say you have spherical metal conductor with a cavity with a positive charge inside, the field inside the cavity isn't zero and will induce an opposite charge/field on the surface of the cavity which will cancel the charge inside and lead to a zero Electric field inside the conductor. the...
  35. B

    Potential inside sphere with empty cavity

    Homework Statement An insulating sphere of radius R , centered at point A, has uniform chagre density ρ. A spherical cavity of radius R / 2 , centered at point C, is then cut out and left empty, see Fig. (a) Find magnitude and direction of the electric field at points A and B. (b) Find...
  36. R

    What Determines the Electric Field Inside a Spherical Cavity?

    Hi, I am dealing with a problem in Electrostatics. Homework Statement There is a sphere with a spherical cavity in it. The sphere itself does not have net charge, but inside the cavity, there is a point charge at the center of the cavity. What's the electric field inside the cavity? Homework...
  37. R

    Surface charge density on a cylindrical cavity

    Hi folks, I am having trouble generalizing a well-known problem. Let's say we have a cylindrical cavity inside a conductor, and in this cavity runs a line charge λ. I would now like to know the surface charge density on the inside wall of the cavity, but with the line charge not in the center of...
  38. F

    Optimizing SISO System with BPF vs Cavity Filter for Interference Protection

    "][/URL]Hi to all, i have a SISO system with microwaves devices. The 16-QAM information is about 20KHz , upconverted at 30 MHz and then at 2462MHz.At the receiver the same procedure, downconverting. After the first LNA i have a BPF fc=2430MHz which has large Bandwidth so it does not protect...
  39. K

    A Charged Sphere with a Cavity

    Homework Statement An insulating sphere of radius a, centered at the origin, has a uniform volume charge density ρ. A spherical cavity is excised from the inside of the sphere. The cavity has radius a/4 and is centered at position h(vector) , where |h(vector) |<(3/4)a, so that the entire...
  40. G

    Separable PDE for electric field in a cavity

    Homework Statement Here is a photo of a page in Laser Physics by Hooker: https://www.evernote.com/shard/s245/sh/2172a4e7-63c7-41a0-a0e7-b1d68ac739fc/7ba12c241f76a317a6dc3f2d6220027a/res/642710b5-9610-4b5b-aef4-c7958297e34d/Snapshot_1.jpg?resizeSmall&width=832 I have 3 questions (I'm a bit...
  41. H

    MATLAB Cavity simulation on matlab with spatially dependent phase

    Hello there, I have been searching for MATLAB simulations that analyze optical cavities and there are some useful codes. Yet, I haven't found codes that analyze what happens to cavit transverse modes if spatially dependent phase is introduced between mirrors Does anybody know if there...
  42. H

    Solving paraxial equation (to get cavity modes)

    Hello, I've been going through some cavity material and attempted analyses regarding transverse modes. Invariably, they always deal with general solutions of paraxial equation and do not have solutions specific to specific cavities I do know that general solutions to paraxial equation...
  43. W

    Transitions on resonance with a cavity.

    I'm not exactly sure what I'm trying to ask, and I'm not very keen on laser physics, so bear with me. If I have a system in an excited state that can decay by spontaneous emission with a certain lifetime, what is the effect of placing it in a cavity with a mode resonant with this transition...
  44. Markus Hanke

    Thin Shell Cavity in General Relativity

    I am trying to understand the implications of the Birkhoff theorem as it applies to a cavity within a spherically symmetric, stationary thin shell. Is the region of space-time within the cavity described by the actual Minkowski metric diag{1,-1,-1,-1}, or is it some other metric with constant...
  45. Saitama

    Magnetic field inside cavity

    Homework Statement A constant direct current of uniform density ##\vec{j}## is flowing in an infinitely long cylindrical conductor. The conductor contains an infinitely long cylindrical cavity whose axis is parallel to that of the conductor and is at a distance ##\vec{\ell}## from it. What will...
  46. O

    Light emission from a hole in a cavity

    Homework Statement Sethna 7.7 Assume that the hole of area A is is on the upper part of the cavity, perpendicular to the z axis. The vertical component of the velocity of each photon is therefore vz= c cos(θ), where θ is the angle between the photon velocity and the vertical. The photon...
  47. M

    Moving a point charge out of a cavity in a conductor

    Homework Statement A point charge q is at the center of an uncharged spherical conducting shell, of inner radius a and outer radius b. How much work would it take to move the charge out to in nity? (fi nd the minimum work needed. Assume charge can take out through a tiny hole drilled in...
  48. F

    How do quarter wave resonant cavities work in duplexers and filters?

    I've been self studying microwave engineering for a little while, and also I work in the radio telecommunications field. I try to relate what I've learned in the book to what I encounter in out in the field. Recently I was studying resonant cavities. From what I thought I understood about...
  49. Darth Frodo

    Calculating Heat Transfer in a Cavity Block Wall with Windows

    Homework Statement A cavity block wall of area 10m2 constructed of 100 mm concrete, 50 mm air gap, 50 mm of polystyrene and a second 100 mm wall of concrete. The wall contains three windows with dimensions of 0.5 m x 0.7 m with glass 4 mm thick. The outside temperature is 5 °c and the inside...
  50. D

    Frequency doubling of monolithic Nd:YAG laser in external enhancement cavity

    1. LiNbO3 is a negative uniaxial crystal. Consider a LiNbO3 crystal used for frequency doubling a laser operating at 1064 nm. The non-linear coefficient is d=3.4x10-23. For the setup considered it is desirable to have a non-linear conversion efficiency of 0.04 %/W, Assume constant fundamental...
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