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. G

    Finding the air cavity resonance of a propane tank for a drum.

    I am going to build a drum out of a propane tank. I think it will be handy to find the resonant frequency of the tank and choose the tuning accordingly so not to pick frequencies that are extremely damped. I have a cavity resonance formula found on hyper physics I am not going to build a...
  2. F

    Electrostatic equilibrium (Sphere with cavity)

    Homework Statement Consider a sphere conductor with a inner concentric sphere cavity. The radius of the inside and outside of sphere are 10 cm and 20 cm. The electric field in a point P, along the outer surface has a intensity of 450 N/C and it is directed out of the surface. When a particle...
  3. P

    What is the Q value for a krypton laser with given specifications?

    Homework Statement Calculate the Q value for a krypton laser with λ=0.569 microns, 0.568m cavity and mirror reflectance of 100% for the rear and 52% for the output window. Homework Equations For a laser cavity=> Q=(4πL)/(λ(1-R1*R2)) The Attempt at a Solution Q= (4*π*...
  4. S

    Electric field inside a cavity

    Homework Statement If I have a solid sphere of radius R and charge density +\rho \, C/m^3 and I then remove a smaller sphere of radius b and is a distance a from the center of the larger sphere, what is the electric field inside the cavity? I get an answer which I think is right. I've look...
  5. I

    Books for tackling articles in Cavity QED and Quantum Optics

    Hi, I am a graduate student with a background more oriented in high energy physics and cosmology but switching to light and matter interaction, more specifically cavity QED and quantum optics. I need to have a working knowledge on those topics, being able to read state of the art articles and...
  6. X

    Finding potential inside the cavity of a Conductor

    Homework Statement A conductor, maintained at a potential V, contains a spherical cavity of radius R. A point charge q is placed at a distance a ( a < R)from the center of the cavity. Find the potential of the electric field in the cavity . Homework Equations I was considering using...
  7. N

    What is the physical significance of dephasing in cavity QED?

    Hi In cQED and the Jaynes-Cummings model, three parameters are usually introduced which describe the atom-cavity system: The radiative lifetime γ, the cavity linewidth κ and the pure dephasing rate 1/T2. However I am not that familiar with the latter parameter. Basically I guess it describes...
  8. C

    Electric field of a sphere whit a cavity inside

    Hi, I calculated the electric field of a sphere of radius r with a volumen density charge \rho and also it has inside of it a spherical cavity and its center is situated in r/2 with radius r/2, so I calculated the electric field of the sphere with the cavity inside and I get E=\frac{\rho...
  9. C

    Counting electromagnetic modes in a rectangular cavity and boundary conditions

    The electric field in a cubical cavity of side length L with perfectly conducting walls is E_x = E_1 cos(n_1 x \pi/L) sin(n_2 y \pi/L) sin(n_3 z \pi/L) sin(\omega t) E_y = E_2 sin(n_1 x \pi/L) cos(n_2 y \pi/L) sin(n_3 z \pi/L) sin(\omega t) E_z = E_3 sin(n_1 x \pi/L) sin(n_2 y \pi/L)...
  10. N

    External Cavity Laser: Ultra Narrow Line Width

    Hello, How does an external cavity laser produce ultra narrow line width when it's larger cavity should reduce the free spectral range and thus introduce more longitudinal modes? Thanks.
  11. B

    Abaqus: Fluid Cavity - Moving cavity under uniform hydrostatic pressure

    Hi Dear All, Hope I can have some suggestions to tackle this weird problem. I have an axisymmetric ball, with CAX8R elements being inflated with hydrostatic fluid elements. Fluid elements surface is put on the internal surface of the ball (defined by picking the surface of the CAX8R...
  12. M

    Fluid Mechanics - find a cavity of a block if it exist?

    Homework Statement You are given a 10cm Cube of aluminum with Density of 2700kg/m is submerged in water and the weight in water is 13N. If a cavity exist how big is it? Homework Equations The equation i used were B = V * P_water * g to find buoyancy. To find the enclosed cavities i...
  13. S

    Energy of e.m waves in a cavity

    Hi there people I'm going through some old notes and have become a bit confused... I'm looking at the energy density of e.m modes in a cavity I have that (energy in the range ω to ω+dω) = (mean number of quanta per mode) x (energy per quanta) x (number of e.m modes in the range ω to...
  14. H

    Why does the cavity in a lead sphere increase on heating?

    There is a spherical lead ball with a spherical cavity. It is heated. The size of the cavity increases. Why does it do so? Also, does it matter what happens to the cavity if it is not present at the centre, but rather a little removed from the centre? Will it remain spherical?
  15. M

    Electric field inside the cavity of a sphere.

    If a conducting sphere having a cavity inside it is placed in an electric field then what will be the field inside the cavity?And is there any charge induced in the cavity?I have many doubt about it give a good discussion about it.. :confused:
  16. I

    Some question on charge inside cavity

    Hi Consider the case of a charge placed inside the cavity in a metal. Let the charge be at A. Assume that the cavity is some weird geometric shape so that one point on the inner surface of the cavity is closer than some other point. Let point B on inside wall be closer to the location of...
  17. C

    Why Is the Magnetic Field Uniform in a Non-Coaxial Cylindrical Cavity?

    Homework Statement We are given an infinitely long cylinder of radius b with an empty cylinder (not coaxial) cut out of it, of radius a. The system carries a steady current (direction along the cylinders) of size I. I am trying to find the magnetic field at a point in the hollow. I am told that...
  18. D

    Time Evolution of Polarized Cavity

    Homework Statement Suppose that a particular x-polarized cavity mode is described, at time t = 0, by the state |ψ(0)> = (1/√2)(|n> + |n+1>) Find |ψ(t)> for t > 0. This is best done in the Schrodinger picture. Evaluate the expectation of the electric field operator Ex and the uncertainty...
  19. N

    Cavity QED Books: Find Your Perfect Read!

    Hi Does anybody know of a good book on cavity QED? It seems that most books only have a small part of a couple of pages covering the subject. Niles.
  20. L

    How do you simulate an isothermal filling of a cavity using Autodesk Mouldflow?

    Homework Statement I have to simulate an isothermal filling of a cavity using Autodesk Mouldflow Insight. Homework Equations The Attempt at a Solution I tried setting the mould temperature to the melt temperature but I do not seem to get a reasonable answer as the cavity will fill...
  21. E

    Charged Sphere with off-center cavity Electric field

    Homework Statement Consider a sphere uniformly charged over volume, apart from a spherical off-center cavity. The charge density is ρ, radius of the sphere is a, radius of the cavity is b, and the distance between the centers is d, d < a-b. (a) Find the total charge and the dipole moment...
  22. E

    Charged Sphere with off-center cavity Electric field

    Homework Statement Consider a sphere uniformly charged over volume, apart from a spherical off-center cavity. The charge density is ρ, radius of the sphere is a, radius of the cavity is b, and the distance between the centers is d, d < a-b. (a) Find the total charge and the dipole moment...
  23. genxium

    Understanding Sound Cavity: A Guide for Greenhands

    Homework Statement No specific question, I'm a greenhand to waves, so when it came to sound cavity, I was just confused how the teacher(in the video lecture,I'm not a physics major) can distinguish which side is a node and which is an anti-node, it seems too fast for me, could anyone give me a...
  24. T

    Wave function of a photon in a spherical cavity

    Hello there, could anyone help me with a certain basic problem in relativistic QM? What would be the wave function of a photon (or generally a particle with zero rest mass) in a spherical 3D cavity, having potential energy V=0 within the cavity and V=k outside the sphere (k>0)? I have been...
  25. H

    Resonant wavelength of a cavity resonator using different internal materials?

    Hello everyone, Recently I have been studying cavity resonators. I noticed that all cavity resonators have air in them, but I was wondering what the effects would be if something other than air was used? For the sake of simplicity let's say we put a dielectric material in it with a...
  26. S

    What causes the size of a cavity to change when a metal plate is heated?

    There's a metal plate with a circular hole/cavity in it. Consider its width negligible. Now the plate is uniformly heated. Textbook says that size of hole/cavity increases along with the dimensions of the plate. But my intuition says dimensions of cavity should increase and size of hole/cavity...
  27. S

    Fabry-Perot Cavity: Frequency Separation Explained

    As "refresher assignment" for the new semester I have been given a selection of very short questions, the only one I am having trouble with is the followng: QUESTION An air-spaced fabry perot consists of two exactly parallel reflecting surfaaces, separated by a distance of 1 cm. What is the...
  28. A

    Solving Maxwell's Equations in Laser Cavity | Tips and Troubleshooting

    Hello guys, I've been trying to solve Maxwell's Equations in a laser cavity, with length L. However I cannot... I've searched over the net to find a proper solution but I couldn't. I started by taking a field E(x,y,x,t)=E0 e(x,y)e-jw te-jb z. I take the phasor E(x,y,z)=e(x,y)e-jb z and...
  29. Amith2006

    Electric field inside a cavity within a sphere

    Homework Statement This question has already been asked before. The electric field inside a spherical cavity carved out of a larger sphere is uniform which I have derived. What I don't really understand is that if you construct a gaussian surface inside the cavity, it wouldn't enclose any...
  30. B

    Electric field of single photon in a cavity

    Homework Statement Assume that there is a single blue photon in a cavity of the size of 10 micrometers. The total energy of oscillating electric fields due to this photon is one half of the photon energy. A. Estimate the magnitude of the electric fields associated with this single photon...
  31. H

    Electromagnetic waves in a cavity resonator

    If EM waves are pumped into a resonant cavity at it's resonant frequency will each incoming wave add it's energy to amplify the wave(s) in the cavity? I know that if you pulse a light source into a circular wave guide and you pulse the light source each time the light wave returns to it's...
  32. M

    Rectangular waveguide cavity - Maximum E field

    Hi, I am trying to calculate maximum E-field strength in a rectangular waveguide cavity resonator at 1.6GHz. The input power is 200W while the resonator should wsupport TE101 mode. cavity dimensions are 0.131mmx0.65mmx0.134mm (WxHxL) having lossy walls made up of copper with conductivity of...
  33. R

    Is there a way to derive Planck's Law without using a cavity?

    It is perfectly possible to derive, for instance, the Maxwell distribution of speeds in a heuristic way with only two things: 1. The Gibbs hypothesis, which says that to count the number of states at speed v you take all the points in phase space between v and v+dv in velocity space. This...
  34. S

    Why is a Cavity Within a Conductor Important?

    This is an excerpt from my textbook. Could someone please help me understand why the line I highlighted in yellow is true? Thanks! :)
  35. X

    Electric Field in a cavity of a dielectric medium

    Homework Statement The polarization charge in the surface of a spherical cavity is -\sigma_e \cos\theta ,at a point whose radius from the centre makes and angle \theta with a give axis Oz. Prove that the field strength at the centre is \frac{ \sigma_e}{3 \sigma_e} parallel to Oz. If the...
  36. L

    Can a Cavity Magnetron Be Used in Reverse to Generate Resonant Frequencies?

    Could a cavity magnetron be done in reverse in a way so that the em waves would interact with the magnetic field and give electrons energy to jump from a cathode to an anode and would any resonant frequencies be involved? I've read some where that this is why metal articles should not be put...
  37. X

    Polarization Charge on the surface of a spherical cavity

    Homework Statement The polarizatiob charge on the surface of a spherical capacitor is -\sigma_e \cos(\theta), at a point whose radius vector from the centre makes an angle \theta witha given axis Oz. Prove that the field strength at the centre is \frac{\sigma_e}{3 \epsilon_0}, Homework...
  38. M

    Project Small Resonant Cavity: 2.4GHz Freq Fundamental Mode

    Homework Statement The problem is: Project the smaller ressonant cavity for which the frequency of 2.4 GHz is the fundamental mode. Homework Equations The problem wants me to calculate the length a, b and c of this "microwave oven" The Attempt at a Solution I'm sorry, but I have...
  39. I

    How do I calculate the temperature at different layers within a cavity wall?

    Hi all I have a revision question I am having some trouble with A cold room has a wall measuring 5.2m by 2.5m. The wall is constructed of 120mm thick brick on the inside, a cork layer 80mm and a 30mm layer ow wood in the outside. the inside temperature is -4ºC and the outside temperature...
  40. H

    Relation between cavity resonance and sound speed

    Our sound will be like "Donald Duck" if we inhale helium gas and the explanation from web is because" The cavity resonances which determine the vocal formats would be raised by the higher sound speed,"(http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe.html). Why cavity resonance raise as...
  41. A

    ELectric field inside a cavity

    Homework Statement Suppose there is a cavity inside a metallic conductor...And say a chrge q is placed inside it...Now a charge -q is induced on the inner metal surface and a chrge q appears outside... Homework Equations The Attempt at a Solution Now i have two questions ...
  42. S

    Electric field in a conductor with an internal cavity

    I'm not entirely sure if this is meant to be in the "advanced physics" section, it's for my undergraduate degree anyway. Homework Statement A conducting sphere of radius R, carries a total charge of q. It is surrounded by an electrically neutral conducting shell with an inner radius, a, and...
  43. M

    Cylindrical electromagnetic cavity.

    Homework Statement A cylindrical electromagnetic cavity 4.8cm in diameter and 7.3 cm long is oscillating. a) Assume that, for points on the axis of the cavity Em=13kV/m. The frequency of oscillation is 2.4 GHz. For such axial points, what is the maximun rate (dE/dt)m, at which E...
  44. R

    Conductors with off-centered cavity

    Suppose we had an uncharged solid spherical conductor with radius R, and some spherical cavity of radius a that is located b units above R, where a+b<R. If we place a charge inside the cavity at the center, how would you quantitatively express the E-field lines outside of the conductor?
  45. M

    Welcome to the Forum! Learn About Cavity Resonance Here.

    hello I am a new member in this forum , and I want to learn well with you...sorry I speak little English,so I use google traductor , i speak french , but with french unfortunately there is a little information! now what is a cavity resonant ? and how to write equations for field within...i...
  46. Q

    Photon Average Energy in a Cavity Resonator

    The rms EM field within a cavity resonator, excited in a single resonant mode by a current probe of fixed rms amplitude, is known to rise linearly with time; eg. http://www.jpier.org/PIER/pier78/15.07090605.Wen.pdf", sections 5.2, 5.3, fig's. 6, 10. (Normally it is a fixed driving voltage...
  47. Q

    Spherical cavity in a dielectric with a point charge inside

    Homework Statement I am trying to find the force acting on a charge placed a distance r0 from the center of a spherical cavity of radius a. The entire cavity is immersed in a dielectric material, epsilon2. Homework Equations The Attempt at a Solution Here's my quandary: I can find the...
  48. A

    Fraction of stimulated photons that escape from a laser cavity

    How to calculate the fraction of stimulated photons that escape from a laser cavity with alpha=0.1 cm^-1 length of cavity=1mm refractive index of laser cavity=3.2 the photons are assumed to be escaping into air so approx refractive index is 1. Im assuming that alpha is some sort of...
  49. R

    Analytical solution for circular cavity under internal pressure

    A book listed the problem infinite circular cavity under internal pressure and said there is a analytical solution for stress and displacements but it didn't give any reference. I have searched many papers and online materials but still couldn't find anything. The closest thing I found...
  50. 1

    MATLAB Finite difference method with matlab- square grid, cavity inside

    Hi, I'm here for help and hope somebody could give a hand on this because I'm noob in this. I'm now constructing a MATLAB program to find Electrical field and potential within a square grid mesh with square cavity inside. like the picture above. I only manage up to this...
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