Van der Waals vs. Casimir Force: Explained

In summary, the Casimir force is a prediction of quantum field theory that occurs when two perfect metallic plates restrict the waves of energy in the vacuum between them, resulting in a pressure difference that pushes the plates together. It is similar to the van der Waals force, but in the Casimir effect, the lifetime of a virtual photon is not long enough to reach the other plate. This can be visualized as a restriction of all possible standing waves in the vacuum. It is also possible for a similar effect to occur between the interior and exterior of the electron cloud of a hydrogen atom.
  • #1
axis de la sal
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the retarded van der waals force is called the casimir force and the diference between them is that in the oscilations in vacumm between to perfect metallics plates if there is a van der waals force virtual photons reach form one plate to the other in casimir the life time of the photon is not enough to the photon to reach the other plate but ok i can understand it but someone could make it more clear .
 
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  • #2
The casimir effect is a fascinating prediction of quantum field theory.

The best way to visualize is to picture the vacuum as consisting of 'waves' of energy of ALL possible frequency. When you put the plates in you RESTRICT the WAVES that can exist within the plates (all possible standing waves).

The RESTRICTION on the waves on the INSIDE, means that there is 'less' waves on the inside than on the outside so in effect you have a pressure difference with less pressure on the interior than on the exterior so the plates are effectively pushed together.

Rich
 
  • #3
is there a casimir type effect between the interior and exterior of the electron cloud of a hydrogen atom?
 

1. What is the difference between Van der Waals force and Casimir force?

The Van der Waals force is an attractive force between neutral molecules or atoms, caused by temporary dipoles in their electron clouds. On the other hand, the Casimir force is an attractive force between neutral objects due to quantum fluctuations in the vacuum between them.

2. How are Van der Waals force and Casimir force related?

The Casimir force can be seen as a consequence of the Van der Waals force on a much larger scale. Both forces are caused by the interaction between fluctuating electric fields, but the Casimir force is a long-range force compared to the short-range Van der Waals force.

3. Can the Van der Waals force and Casimir force be repulsive?

Yes, under certain circumstances, both forces can be repulsive. For example, when the distance between two objects is small enough, the Van der Waals force can become repulsive. Similarly, with the use of specially designed materials, the Casimir force can also be made repulsive.

4. What are some real-world applications of Van der Waals and Casimir forces?

The Van der Waals force is involved in many everyday phenomena, such as the cohesion of water molecules, adhesion of gecko feet to surfaces, and the formation of droplets. The Casimir force has been utilized in the development of micro- and nanoscale devices, such as tiny accelerometers and actuators, and also plays a role in the stability of colloidal suspensions.

5. How do scientists study and measure Van der Waals and Casimir forces?

Scientists use a variety of experimental techniques, such as atomic force microscopy and surface plasmon resonance, to measure the strength and distance dependence of Van der Waals and Casimir forces. Theoretical models, such as the Lifshitz theory, are also used to understand and predict these forces between different types of materials.

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