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. S

    Calculate sound pressure inside a cavity

    How do I calculate sound pressure inside a channel. I have a channel of 40 mmx 40 mm cross sectional area. I have placed a sound source on one of the side wall that resonates at 50 Khz. I know the voltage required to drive the transducer. The transmit voltage response of the transducer is 110...
  2. S

    Will soldering be an effective method for constructing a microwave resonator?

    So I'm about to construct a TE102 microwave resonator from folded copper sheeting. I'm planning to fold a U shape and join it to the last side with silver solder. Is this going to work well? I'm planning on making good physical contact through accurate folding, and then securing the pieces...
  3. T

    Fabry Perot Cavity - phase difference?

    Hi, I'm having trouble understanding where the formula (appearing in my notes or Wikipedia) comes from. One can read on Wikipedia: The phase difference between each succeeding reflection is given by \delta = \frac{2 \pi}{\lambda}2nlcos\theta Where n is refractive index inside cavity, l...
  4. V

    How Does Plasticity Theory Apply to a Spherical Cavity in Mohr-Coulomb Material?

    this is a short abstract of problm i m working upon..so please help ..suggestions are kindheartedly welcome... a spherical cavity of radius R in a Mohr-Coulomb incompressible material. properties are defi ned by Young's modulus E, Poisson's ratio v, internal angle of friction (shi) i...
  5. Y

    Calculate current in a cylinder with a hollow cavity

    Homework Statement I got this problem (Sectional image of a cylinder): http://img715.imageshack.us/img715/3448/cylinder.jpg Besides that I know that the cylindrical conductor is infinite long, and the same is the cavity. And through the conducting material there is a current density that is...
  6. M

    Uniform Electric Field in Cavity of Solid Sphere

    Homework Statement A charge q is uniformly distributed over the volume of a solid sphere of radius R. A spherical cavity is cut out of this solid sphere, and the material and its charges are discarded. Show that the electric field in the cavity will then be uniform, of magnitude...
  7. T

    Vector potential in cavity of arbitrary shape

    we know that vector potential in a resonator satisfies the equation \intA(\lambda)A^{*}(\lambda^{'})dV=4\pic^{2}\delta_{\lambda\lambda^{'} So how about in cavity of arbitrary shape? Does this equation still valid? Thanks!
  8. J

    Gauss Divergence theorem to find flux through sphere with cavity.

    Homework Statement Use the divergence theorem to find the outward flux of a vector field F=\sqrt{x^2+y^2+z^2}(x\hat{i}+y\hat{j}+z\hat{k}) across the boundary of the region 1\leq x^2+y^2+z^2 \leq4 Homework Equations The Gauss Divergence Theorem states \int_D dV \nabla \bullet...
  9. S

    Electric field inside a cavity within a uniformly charged sphere

    A uniformly charged sphere (center 0,0) with radius 2a and volume charge density \sigma has a cavity within it (center 0,a) with radius a. Show that the electric field within the cavity is uniform and Ex=0 Ey=\frac{a\sigma}{3\epsilon} where \epsilon is the permittivity of free space. Hi, I...
  10. L

    Cavity Resonators by two waveguide coaxial adapters

    One of my professors made an X-band cavity resonator by putting together, end to end, two X281A coaxial waveguide adapters (n-type) with cut center pins. It works pretty well - but I need some more information. Does anyone know where can I find some more information on this setup...
  11. J

    Electric field sphere with inner cavity

    Homework Statement I have : Spherical conductor of radius=x; Spherical conductor has a inner cubic cavity of side = b; inside the cubic cavity we have a charge = y; the surface of the sphere has a charge density = z; I need to calculate the electric field at some point g, where g>r...
  12. A

    Does Energy Decay Occur in Sealed Metal Boxes with Excited Resonant Modes?

    Hey there, I recently solved for the resonant modes in a 3d metal box. Thats nice, but I was wondering about how to actually excite the modes (its a sealed metal box) Supposing I actually excited these modes by shining incident em radiation such that a portion [of the incident wave]...
  13. E

    Electric Field in a tiny cubical cavity within three piled disks of charge.

    Homework Statement A charge distribution has the shape of a very large disk of thickness 3d. This disk has three layers of uniform densities \rho_{1},\rho_{2},\rho_{3} and thickness d each one. Within the layer with density \rho_{2} exists a tiny cubical cavity in such a manner that two of...
  14. J

    Electric field inside a cavity of a uniformly charged sphere

    Homework Statement Well, there are two problems, both of which would allow me to receive extra credit in my college physics class! Both are rather descriptive, so I have linked an image to it. http://img87.imageshack.us/img87/9570/1000497y.jpg" Homework Equations For the first, I was...
  15. S

    New Superconducting RF Cavity: Potential for EMdrive Propulsion?

    Here's an interesting article about a new breakthrough in the manufacture of a superconducting radio-frequency cavity: http://nextbigfuture.com/2009/09/superconducting-radiofrequency-cavity.html If this new cavity were tested for EMdrive purposes, could it reveal a new mechanism for...
  16. N

    Power dissipated in a cylindrical cavity due to a current carrying filament

    Homework Statement A cylindrical cavity oriented along z axis with length of 2 m has a filament in it upon which a current of 10 A is impressed. Cavity is perfectly conducting whereas it is filled with lossy dielectric. Electric field on the cavity is given as: E=-z(i+j). One has to...
  17. P

    Air vibrating in a cylindrical cavity

    The diagram accompanying this post shows a cylindrical column bored at right angles to a flat surface. Let’s say the material is a block of brass with a hole drilled in it. The arrow represents a fast moving stream of compressed air. As the air passes over the top of the column a high pitched...
  18. A

    Calculate the Velocity of a Mass released in a Sphere Cavity

    Q6. Inside a fixed sphere of radius R and uniform density d ,there is a spherical cavity of radius R/2 such that the surface of the cavity passes through the centre of the sphere . A particle of mass m is released from rest at centre B of the spherical cavity. Calculate the vel. withwhich the...
  19. A

    How Is Charge Distributed in a Conductor with an Internal Cavity?

    1. The Question An isolated conductor of arbitrary shape has a net charge of +10\times10^{-6}C. Inside the conductor is a cavity within which is a point charge q = +3\times10^{-6}C. What is the charge on the outer surface of the conductor? 2. The attempt at a solution On cavity wall...
  20. I

    Resonance frequency of a magnetron cavity

    Is the resonance frequency of a magnetron cavity purely a function of its geometry? Thanks!
  21. I

    Why is it that an antenna/waveguide is only connected to one cavity

    Why is it that an antenna/waveguide is only connected to one cavity in the magnetron, such as in a microwave? Are the resonating RF waves in the other cavities wasted then? Thanks! Edit: Also, are magnetrons always thermionic diodes?
  22. maverick280857

    Quality Factor of Cavity Resonator

    Homework Statement Prove that the quality factor of a rectangular cavity resonator which is filled with a lossy dielectric but has perfectly conducting walls, is given by Q = \frac{1}{\tan\delta} where \tan\delta is the loss tangent, i.e. the ratio of the imaginary part of the dielectric...
  23. D

    Solving the Photon Lifetime in a Cavity: A Beginner's Guide

    could someone help me get started on a problem solving the photon lifetime in a cavity? i have 4 optical paths
  24. C

    Calculate Magnetic Induction in Cylindrical Hole w/ Uniform Current

    Question: An infinite cylindrical wire with radius 2R caries a uniform current density J=Jz, except in an infinite cylindrical hole parallel to the wires axis. The hole has a radius of R and is tangent to the exterior of the wire. Calculate the magnetic induction B everywhere inside the hole...
  25. P

    Electric Field Uniformity in a Sphere with Cavity

    Homework Statement A charge q is uniformly distributed over the volume of a solid sphere of radius R. A spherical cavity is cut out of this solid sphere and the material and its charge are discarded. Show that the electric field in the cavity will then be uniform, of magnitude kqd/r^3, where...
  26. L

    Calculating Resistances of a Cavity Wall

    Hi, I am trying to work out the resistances for the following cavity wall. I am having to work backwards. I have the U value, which is 0.48. The brickwork is 103mm, the insulation in cavity is 50mm, lightweight concrete block is 100mm and plaster board is 13mm. I know total thickness...
  27. S

    Electric Field in Cavity of Conductor: Explained

    Homework Statement Show the electric field inside an empty cavity in a conductor is zero, even if there is a charge outside the conductor. If a charge is placed inside the cavity, will there be an electric field outside the conductor. Explain Clearly. Assume that both the conductor and cavity...
  28. X

    Field strength giving rise to a polarization charge of -s.cos(theta) on a cavity

    Hello, I'm learning EM from Bleaney & Bleaney and got stuck on Ex2.1 (can do Ex2.2-2.7, though...) - If the polarization charge on the surface of a spherical cavity is -s.cos(theta), prove that the field strength at the centre is s/3e0. If I expand V(r) within the cavity as A.r.cos(theta) +...
  29. V

    Probability of finding a spherical cavity of a radius in proteins

    Homework Statement The hydrophobic effect is important in stabilizing the folding of globular proteins. This is because of the drive to reduce interfaces between hydrophobic side chains and the solvent, usually polar water. One can estimate the contributions from hydrophobic forces to protein...
  30. I

    Magnetic field inside the cavity of a long straight wire

    Homework Statement A long straight wire of radius R carrying a current I has a circular portion of radius a cut out at a distance d from the center, as shown in the picture. Find the magnetic field inside the cut-out portion. Homework Equations magnetic field equation (I can't write it...
  31. Phrak

    Understanding Energy Partition in Laser Cavity: Molecules vs. Radiation

    A laser cavity consists of a couple mirrors, a bunch of metastable molecules and some radiation. What's the partition of energy between molecules and radiation at equilibrium?
  32. F

    What parameters determine the volume and depth of the cavity?

    cavity on a water surface A vertical air jet from a straw produces a cavity on a water surface. What parameters determine the volume and depth of the cavity?
  33. M

    Understanding 2D Driven Cavity Flow: Explanations and Applications

    hi everybody I have one doubt as what is the meaning of 2d driven cavity flow?
  34. P

    Solving EM Wave Emission from Cavity at T: Power per Unit Area

    Homework Statement Basically, the problem states that a cavity at temperature T is emitting EM waves isotropically in all directions (with frequency distribution of Planck's Law). If the time averaged density is <e>, find the value of d<S>/dw where w is the solid angle and the quantity is the...
  35. M

    Electric field inside a cavity within a uniformly charged sphere problem

    Homework Statement A uniformly charged sphere (center O1) with radius a and charge +Q has an off-center cavity within it (center O2) with radius b. Show that the electric field within the cavity is uniform and is directed along the line of centers, according to the equation: \vec{E} =...
  36. S

    Gauss' Law - Sphere with spherical cavity

    Gauss' Law - Sphere with spherical cavity - Please help Homework Statement A sphere of radius 2a is made of nonconducting material that has a uniform volume charge density . (Assume that the material does not affect the electric field.) A spherical cavity of radius a is now removed from the...
  37. C

    Spherical Cavity in Dielectric Subject to Uniform Field

    Homework Statement The polarization charge on the surface of a spherical cavity is - \sigma_e cos(\theta) at a point whose radius vector from the centre makes an angle \theta with a given axis Oz. Prove that the field strength at the centre is \frac {\sigma_e}{3 \epsilon_o} parallel to...
  38. E

    In a cavity 12.5 cm by 3.9 cm, with Y being 12.5 cm and X/Z being 3.9,

    In a cavity 12.5 cm by 3.9 cm, with Y being 12.5 cm and X/Z being 3.9, how would you calculate the resonance for that internal volume. The volume is filled with air and the sidewalls are not rigid. This is also assuming that one end is open. I can, of course, give more information if it's...
  39. P

    Eletric field within a cavity of a cylinder.

    Homework Statement Considering a cylinder of radius, R, and length D with uniform charge density p containing a spherical cavity of radius R/2. Find the field in the cavity. The cavity sits on one side of the cylinder so that it's diameter spans from the concave face of the cylinder to the...
  40. I

    What Determines Surface Charge Density Inside a Cavity: A or B?

    The figure shows a cuboidal shaped conductor inside which there is an ellipsoidal cavity. The center of the cavity is at the center of the cuboid. Link to figure: http://www.picscrazy.com/view/1qtB9 A charge qo is kept at the center of the cavity. I am showing two positions 'A' and 'B'. MY...
  41. C

    Tunable External Cavity Diode Laser

    http://optics.ph.unimelb.edu.au/atomopt/publications/littrow_rsi_vol72_p4477_2001.pdf The picture of the ECDL I explain can be found from the above web site. The purpose of piezo is to change the cavity length of the diode laser, so that the wavelength can be varied. From the picture...
  42. H

    What is the Difference Between a Microwave Cavity and Chamber?

    hi , I am confused with these two terms microwave cavity and microwave chamber . Some say that the microwave chamber inside which food gets cooked acts like a resonant cavity ( which I believe is not true ) because resonance must best be avoided inside the chamber .Resonance I think...
  43. R

    What is the radius of the spherical cavity?

    An irregularly shaped chunk of concrete has a hollow spherical cavity inside. The mass of the chunk is 38 kg, and the volume enclosed by the outside surface of the chunk is 0.025 m3. What is the radius of the spherical cavity? I think you have to find the surface area to solve for the radius...
  44. S

    How Does a Cavity Inside a Charged Sphere Affect Electric Field Calculations?

    An insulating sphere of radius 5.00 cm , centered at the origin, has a uniform volume charge density 3.05 uC/m^3 . There is a spherical cavity cut out of its center of radius 2.00 cm. Well i know to use Gauss' Law: Φ = ∫E∙dA = Q/ε where Φ is the electric flux, E is the electric field, dA...
  45. cepheid

    Fabry-Perot Cavity: Energy and Round Trip Phase Dynamics

    Hi, I know this is dumb question, and I should be able to figure it out and move past it, but I can't. The optics book I have begins its treatment of Fabry-Perot cavities by considering the case of an undamped optical resonater (perfectly reflecting mirrors). Here's a quote from it: If that...
  46. B

    Laser Cavity Length Calculation

    Hi, So I have a lab question for which I have to drive a formula to find the optical cavity length of a laser, L . I have results from testing the fringe patterns when I move one of the mirrors in a Michelson interferometer. It shows the typical \frac{\sin x}{x} pattern. To find the cavity...
  47. X

    Does Clock Speed Vary with Gravitational Potential Inside a Spherical Cavity?

    Inside a spherical cavity centered at the Earth's center, is the space-time curvature is 0 or not 0? Would the clock run more slowly?
  48. deccard

    The length of laser's optical cavity. Multiple of wavelength?

    In order to produce coherent laser light is it necessary that the length of optical cavity between the mirrors is a multiple of the wavelength of laser light? I cannot see how otherwise the laser been could bee coherent. On the other hand I don't see how it is possible to place the mirrors with...
  49. D

    Insulating Spherical Charged Solid with a Cavity

    Homework Statement A point charge of -2.09*10^(-6) C is located in the center of a spherical cavity of radius 6.54 cm inside an insulating spherical charged solid. The charge density in the solid is 7.36×10^(-4) C/(m^3) . Calculate the magnitude of the electric field inside the solid at a...
  50. H

    Electric field in an empty cavity

    Homework Statement The electric field inside an empty cavity in a conductor is zero. Is this statement true no matter what the shape of the cavity? Why or why not? Homework Equations Electric field equation. E = kQ / R^2 The Attempt at a Solution I can't seem to figure out if this...
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