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. A

    RF cavity shunt impedance, PD and input power

    I still did not understand this from my previous threads, what is the way to determine the instantaneous voltage across the cavity plates at any given moment, in a klystron I suppose the voltage would be proportional to the arriving electron bunch density which would determine the overall bunch...
  2. Danny Boy

    A Query about an article on quantum synchronization

    I am currently studying this paper on quantum synchronization. The first page gives an introduction to synchronization and the basic setup of the ensembles in the cavity. My query is on the second page where the following statements are made. Can anyone see why the implication is that all...
  3. Danny Boy

    Quantum synchronization in a cavity

    I am currently studying quantum synchronization. I am reviewing a https://www.researchgate.net/publication/251232415_Quantum_Synchronization_of_Two_Ensembles_of_Atoms which describes quantum synchronization of two ensembles in a cavity. As such, I have a query regarding a cavity physics related...
  4. GhostLoveScore

    I Trouble with cubical cavity radiation

    Hi everyone I have some trouble understanding quantum physics. Here is a scan from the book from Eisberg and Resnick Here is how much I understand. This is radiation inside cubical cavity, λx/2 is distance from two nodes of component x of the radiation. Same goes for y and z components. In the...
  5. J

    I Relation between spectral radiance and density of cavity

    Hi, my teacher showed us how we can derive de relation between spectral radiance and density of cavity (of a black hole), but I have a doubt. This is the equation of the energy that are coming from definited directions by the intervals of angles θ and Φ with frequency in a determined interval...
  6. V

    How Can I Calculate the Number of Photons in a Laser Cavity?

    Homework Statement The laser cavity is formed by two mirrors separated by 15 cm. One of the mirrors has an ultra-high reflectivity and the output mirror has the much lower reflectivity of 99.5 %. How many photons are there in the cavity?[/B] The power of the laser is 1mW and the wavelength is...
  7. S

    I Effect of Roughness on Cavity Resonator Spectrum

    If we start with a light mode in a perfect cavity, in a state such as ##1/2\hbar\omega_m + N\hbar\omega_m## , what happens if we introduce a small amount of roughness (something like 0.5% to 5% of ##\lambda_m##) ? Would it create a cluster of similar but non-degenerate discrete modes around the...
  8. T

    Wavelength of a laser within an optical cavity

    1. The problem statement, all variables and given/known date Homework Equations $$\delta v=\frac{c}{2nL} \:[1]$$ $$N=\frac{\Delta v}{\delta v}=\frac{2nL\Delta v}{c} \:[2]$$ The Attempt at a Solution I am having trouble with question 5, but have come to realize I think my cavity length is...
  9. cookiemnstr510510

    Conducting Sphere With Cavity E-field / Gauss' law

    Homework Statement You have a conducting sphere that is in equilibrium, it has a cavity in it with positive charge +q. If you bring another charge +q2 near the outer edge of the conductor does the total surface charge on the wall of the cavity, q(int) change? There is an image attached that...
  10. cookiemnstr510510

    Electric field sphere calculations with a hollow cavity using Gauss' law

    Homework Statement A spherical cavity is hollowed out of the interior of a neutral conducting sphere. At the center of the cavity is a point charge, of positive charge q. (picture attached) a)What is the total surface charge q(int) on the interior surface of the conductor (i.e., on the wall of...
  11. Twigg

    Entropy Production in an Optical Cavity?

    Howdy, Say you've got two highly reflective mirrors forming a cavity. Some broadband light goes in, but only narrowband light comes out. Entropy is definitely decreased as far as the photons are concerned. Where does it go? This has been bugging me. I have a partial solution I was hoping you...
  12. Domenico94

    I How does a fluid behave inside of a spherical cavity?

    Suppose you have a spherical cavity, with a flow of a fluid ( in particular water), entering it from one side. What will happen to this flow? Will it create turbulences? Will speed increase? Will eventual waves entering the cavity be reflected, so creating waves with bigger amplitude? Suppose...
  13. C

    I Cylindrical Microwave Cavity Resonator: Speed of Light Dependency?

    Does the operation of a cylindrical microwave cavity resonator as described here, https://en.wikipedia.org/wiki/Microwave_cavity, depend on the speed of light being isotropic along the cylinder axis?
  14. B

    Cavity inside a current carrying conductor

    suppose there is a cavity inside a current carrying conductor.if anyone is inside the cavity he will be electrified or not?what's the explanation of this problem?
  15. H

    Quantum QED textbook that covers QED cavity and Purcell effect

    Dear all, I am looking for an introductory QED textbook (or quantum optics if not) that also covers QED cavity and Purcell effect in one of its chapters. I am not planning to extensively understand every single detail about QED cavity and Purcell effect since I am not a physicist and I don't...
  16. Manolisjam

    Non-conductve sphere with cavity -- find Electric field

    I have a non conducting sphere with a charge ρ=A/r per uni vollume A is constant. suppose there is a cavity in the centre and within a particle of charge q. i want to find the E inside the sphere in respect with r. Homework EquationsThe Attempt at a Solution for radius equal of the cavity i get...
  17. H

    Number of Photons inside a Laser Cavity

    << Mentor Note -- thread moved from the technical forums, so no Homework Help Template is shown >> Let's say you have a laser cavity with two mirrors at either end, one is considered 100% reflective, the other 99.9%, so that a wave beam is emitted through this lower reflectivity mirror. I know...
  18. kal

    I Trouble understanding the idea of a cavity radiator being a Black Body

    I have been trying to understand the role of a cavity as a black body radiator in the derivation of planks black body radiation law but it has left me with 5 main questions: 1. If an object is a perfect absorber it must also be a perfect emitter, meaning that (allowing for a cavity not being a...
  19. M

    Longitudinal/transverse modes in optical cavity (resonator)

    I am learning about lasers and trying to clear up some blurry concepts in my head so I am not necessary using heavy math for description here so please bear with me. Let's take EM field in a rectangular box with walls that are perfect conductors (optical cavity). EM field distribution inside...
  20. Pushoam

    Electric field inside a cavity in a dielectric

    Homework EquationsThe Attempt at a Solution A)[/B] In the spherical cavity, let me have a Gaussian Spherical Surface around the center. Applying Gauss' s Law for dielectrics, ##\oint _S\vec D⋅ d \vec a = Q_{f_{en}} ## Due to the symmetry of the problem and ## Q_{f_{en}} =0## , ## \vec D = 0...
  21. Leonardo Machado

    Cavity in a dielectric material

    Hello friends. If i have a dieletric material ( w/ a hole) and apply an uniform eletric field on it, the eletric field in the hole will stay null ? Peace.
  22. F

    A Rajlich's Hypothesis - Ultrasonic Cavitation

    'Rajlich's Hypothesis is a physical hypothesis with a significance for geology. There exist macroscopic white lamellae inside quartz and other minerals in the Bohemian Massif and even at another places in whole of the world like wavefronts generated by a meteorite impact according to the...
  23. R

    Electric field in a cavity in a spherical charge density

    Homework Statement A uniform spherical charge density of radius R is centred at origin O. A spherical cavity of radius r and centre P is made. OP = D = R-r. If the electric field inside the cavity at position r is E(r), the correct statement is: 1)E is uniform, its magnitude is independent of r...
  24. Spinnor

    B Energy in microwave cavity quantized?

    Consider the microwave cavity used in a particle accelerator to accelerate particle bunches. Before a bunch of particles enters the microwave cavity can we, if only in principle, quantum mechanically describe the state of the microwave cavity as a proper sum of microwave photon number states...
  25. M

    I Can a Half Dipole Antenna Function Inside a Resonant Cavity?

    Hi , what happen if a half dipole linear antenna is placed inside an electric conducting resonant cavity? The cavity itself is the conductive ground of the half dipole antenna. How can I solve such problem in which the cavity works as resonant cavity and it is part of the antenna itself? Cheers...
  26. Emmanuel_Euler

    Medical Oral cavity temperature vs rectal temperature

    Hello Guys How are you?? Today i was studying physiology Body temperature measurement and i saw in general and in normal conditions that the oral cavity temperature is lesser than rectal temperature but why the oral temperature is lesser than rectal temperature?? And what is the reason?
  27. Daniel Petka

    B Quantum Tunneling and Heat Distribution in Laser Cavities?

    What if I replaced the half transparent mirror in a laser cavity with a 100% reflective mirror? -would all photons escape due to the quantum tunneling effect? -would the mirrors melt? Thanks :biggrin:
  28. B

    I Progressive Cavity Pump backspin

    I need an equation to give me the backspin speed in HZ and the torque applied to motor from back spin from a given oil well. The VFD given me the rod torque during forward run. J = 706 lbs-ft. J = F * D D= 7300 ft = Length of the rod J = Jm - Jf -Jb +Jten so I am not sure how to do this ... can...
  29. J

    Charge on a cavity wall and Gauss' law

    Homework Statement An isolated conductor has a net charge of +14.0 × 10- 6 C and a cavity with a particle of charge q = +4.30 × 10-6 C. What is the charge (a) on the cavity wall and (b) on the outer surface? Homework EquationsThe Attempt at a Solution So I understand that B is just adding the...
  30. O

    I Calculation of negative energy density in a Casimir cavity

    Hello, I would like to know how to calculate the negative energy density in the region between two Casimir plates, given a distance between two parallel plates. Thanks, much appreciated!
  31. J

    Electric field inside a cavity

    It is a simple arrangement. Imagine that we have an empty cubic box. Outside the box the electric potential is infinite. Imagine that you put an electric charge at the geomectric center of the box. What is the field around this charge? In other words, the tool I have to calculate the field...
  32. K

    Number of modes in Cubic Cavity

    Homework Statement Calculate the number of modes in a cubic cavity of length a=2.5 cm in the wavelength interval (λ1,λ2) where λ1=500 nm and λ2=501 nm. What's the total energy which radiates from the cavity if it's kept at a constant temperature of T=1500 K. Homework Equations I imagine these...
  33. Tspirit

    How to deduce the solution of normal modes of a cavity?

    Homework Statement In the book "Quantum Optics" written by Scully and Zubairy, there is an equation (1.1.5). The equation is presented directly and not explained how to be deduced. The content is as follows. Homework Equations The Attempt at a Solution I know the solution should have the form...
  34. 1

    Center of mass of a sphere with cavity removed

    Homework Statement A solid sphere of density ##ρ## and radius ##R## is centered at the origin. It has a spherical cavity in it that is of radius ##R/4## and which is centered at ##(R/2, 0, 0)##, i.e. a small sphere of material has been removed from the large sphere. What is the the center of...
  35. M

    I Probability of one-photon loss from a cavity

    Why is the probability of one-photon loss from a cavity in the time interval ##[t, t+\delta t]## is: ##\kappa \delta t\langle \psi(t)| \hat{a}^{\dagger}\hat{a} |\psi(t)\rangle## where ##\kappa## is the decay rate. It looks like the Fermi Golden rule but it's not exactly it.
  36. A

    Mutilple beam reflection question in Fabry-Perot cavity

    Homework Statement Just having some trouble with a question about Fabry-Perot intereferometers. Here's the question: a) Consider a beam of light undergoing multiple reflections in a Fabry-Perot cavity between two surfaces, both with reflectance R, and with no absorption. Homework Equations...
  37. dumbdumNotSmart

    Electric Field in a cavity of a charged sphere

    NOTE: Other threads suggest solving it with Gauss' Law. I'd like to see an approach through direct integration, no full followthrough necessary.. 1. Homework Statement Consider a sphere with a uniform distribution of charge ρ (ro). Inside the sphere is a cavity (spherical). Calculate the...
  38. P

    A Achieving q-switching through cavity stability manipulation

    Does anyone know if there's any q-switching technique that makes use of an unstable resonant cavity (or some kind of switching of the cavity between stable and unstable) to achieve the pulse output?
  39. K

    B How Many Layers of Aluminum Foil Are Needed for a Resonant Cavity?

    I want to build a Resonant Cavity to play with frequencies around 100-700 mhz. I'd like to try different shapes, so I was thinking in using a cheap malleable material like aluminum foil. Questions: - I think one layer of aluminum foil might be too thin.. If I paste a couple of layers will do...
  40. Ryan Reed

    How calculate iris radius and cavity radius in accelerator?

    In linear accelerators that use a disk loaded structure (traveling wave), how would you calculate the iris(disk hole) radius, cavity radius, and disk thickness according to the wavelength
  41. Ryan Reed

    B How would you calculate RF cavity dimensions?

    In a linear accelerator that use cavities and microwaves or radio waves to accelerate particles, how would one find dimensions such as cavity openings, cavity size, length between cavities, etc.
  42. emeriska

    Electrodynamic - Spherical cavity in dielectric

    First, sorry if something is not totally clear, I'm translating physics term the best I can! 1. Homework Statement A sphere or radius a of permittivity ε2 is placed in a dielectric ε1. Without the sphere, we would have E = E0. We want to find the solution to this problem when ε2 = 1...
  43. ELiT.Maxwell

    Point charge inside a electrically neutral cavity in conduct

    bear with me, i know that this question has been asked many time , but i would like a definite answer, now, starting off the external charge density on the outer surface of sphere WILL be uniform by unique solution of Laplace equation and letting the sphere be huge, so, electric field due to...
  44. W

    Atomic Spontaneous Decay in Spherical Cavity

    hello, I am studying spontaneous decay of an atom in spherical cavity - but I am not getting any good book on that can anyone help me in this regard. thanks wasi
  45. Lagraaaange

    (Thermo) Radiation in Cavity. Work and Compression?

    Homework Statement U = u(T)V; P=u(T)/3 a. Find (ds/dt)v and (ds/dv)T in terms of u. Ans. (ds/dt)v = 1/T[du/dt] and (ds/dv)T = 1/T[du/dv + P]...Correct b. Show that u(T) = Const*T^4 equate partials above and integrate...Correct c. Find a Relation between V and T during adiabatic compression or...
  46. S

    B Large Casimir Cavity: Can Its Effect Be Enhanced?

    Assume that one builds a Casimir cavity in the traditional manner, with closely spaced walls. We know the Casimir Effect becomes more pronounced the closer the walls are spaced. Now, if one were to build six such Casimir cavities, and assemble them into a box, would the same effect be noticed...
  47. A

    Charge placed in a cavity in a conductor

    If a conductor has a cavity in it and if a charge is placed in the cavity, then will the electric field inside it be zer
  48. C

    Wavelength/Frequency inside a cavity

    http://www.cengage.com/resource_uploads/static_resources/0534493394/4891/Ch03-WebAppendix01.pdf I've been doing some reading and I came across a mathematical step that is confusing me. Could someone explain to me how they get from equation 3.45 to equation 3.46 in the link that I have posted...
  49. S

    What a different single-mode-cavity and 'single'-mode-cavity?

    Hi, I'm Sungdae studying in Korea. In common, making a energy state in the photonic energy gap. but i don't know exactly what a different single-mode-cavity and 'single'-mode-cavity? Thanks
  50. Rene Manzano

    Solid conductor sphere with cavity inside

    Hi, this is my modified post since I've been told that I have to use certain format. I hope this is good now. Homework Statement Copper (conductor) sphere of radious R with an spheric bubble inside placed at distance c from the center, with radius b. The metalic sphere has charge Q.Homework...
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