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Solid State Physics
Solid State Physics is the branch of physics that deals with the physical properties of solid materials, especially the electromagnetic, thermodynamic, and structural properties of crystalline solids.
813 Questions
Does metallic bonding involve free-floating electrons?
Yes, metallic bonding involves free-floating electrons that are delocalized and are able to move freely throughout the metal structure. These mobile electrons are responsible for many properties of metals, such as electrical conductivity and malleability.
The fundamental equation which gives a simple relation among the wavelength of the X-rays, the inter planar distance in the crystal and the angle of reflection, is known as the Bragg's equation.
2dsin θ = n λ
Some applications of Bragg's equation are:
- Structures of solids are determined by X-ray diffraction method.
- Structures of complex substances such as proteins and nucleic acids are also determined by this method.
What is the property of metals that allow them to be rolled without breaking?
Metals have a property called malleability, which allows them to be rolled into thin sheets without breaking. This property is due to the way metal atoms are arranged in a repeating pattern, which allows them to deform plastically without fracture.
How are sound waves modulated to electic waves?
First step - Sound waves are converted to electricity with a microphone, there are four major technologies for achieving this
1. Dynamic - the sound waves cause a diaphragm to vibrate, which moves a coil of wire inside a magnetic field. This motion generates a very small electrical wave across the ends of the wire coil.
2. Piezzo
or crystal - Utilises the characteristic of certain crystals to generate electricity when pressure is applied, in this instance the pressure is applied via the vibrating diaphragm.
3. Carbon - Probably the oldest form of microphone which consists of a small canister of carbon granules of the consistency of talcum powder. The diaphragm in this case changes the pressure on the granules which alters the electrical resistance of the microphone. Rather than generate electricity this type of microphone forms part of the circuit of another device (amplifier, radio transmitter, telephone etc.
4. Electret
or Condenser or capacitor - Similar in some respects to the carbon microphone, this version utilises the characteristic
of some dielectric materials to alter the capacitance of the device. Most modern electret
microphones include a small pre-amplifier
so that the output of the microphone appears to generate electricity.
Second Step. - these electrical signals go through various amplifiers, mixers etc and eventually wind up at the modulator. Here the signal is combined with a carrier wave (the frequency to which the radio, TV etc is tuned). There are 2 major forms of modulation.
Amplitude Modulation (AM) where the amplitude (size, height, volume) of the carrier changes with the signal and the frequency of the carrier is unchanged.
Frequency Modulation (FM) where the frequency of the carrier changes with the signal and the amplitude is unchanged
What is the shape of ice cube at zero gravity?
At zero gravity (or the microgravity environment of the International Space Station) the high surface tension of a water droplet would pull it into a sphere. If left undisturbed (no waves of motion to distort its basic shape) and allowed to freeze while not in contact with the any of the walls of its container, it would form a near-perfect ice sphere.
However, that same surface tension would, if it came into contact with one of the freezer's walls, cause it to stick: resulting in a part-curved, part-flattened lump that would need to be scraped or pried away.
What is the microstructure of aerogel?
Aerogel has a nanoporous, highly porous structure made up of interconnected clusters of nanoparticles. It has a very low density, with up to 99.98% of its volume being air. This structure gives aerogel its unique properties such as being lightweight, highly insulating, and having a high surface area.
What filter can be used to filter sound waves of 50hertz from a signal?
A notch filter can be used to filter out specific frequencies, such as 50 Hz, from a signal. This type of filter is designed to attenuate a specific narrow band of frequencies while allowing other frequencies to pass through unaffected.
Is a marshmallow considered a amorphous solid?
Yes, a marshmallow is considered an amorphous solid. Amorphous solids lack a crystalline structure and have a disordered arrangement of molecules. Marshmallows have a soft and squishy texture, characteristic of amorphous solids.
What evidence is there to confirm band theory in solids?
There are several pieces of evidence dealing with electrical, optical, mechanical, and thermal properties of solids. To list a few:
- The relationship between conductivity and temperature for metals and semiconductors.
- The normal and quantum Hall effects.
- Optical absorption spectra.
- The elastic moduli of metals and semiconductors.
Can you change the mass of a substance if you distort its shape?
The mass of a substance is not dependent upon the shape of the substance - it is directly related only to volume through its density. Therefore, just because you squash a cube of something into a flat oval, the mass of the substance shouldn't change because the overall volume hasn't changed.
Steam has the most energy as its particles are in the gaseous state and move faster than particles in liquid water or ice, which are in the solid or liquid state respectively. Freezing water has a similar amount of energy as liquid water since they are at the same temperature.
Do liquid particles gain energy when they are frozen?
Yes, when liquid particles freeze, they release energy in the form of heat to their surrounding environment. However, individual particles do not gain energy during the freezing process, but rather lose energy as they transition from a higher energy liquid state to a lower energy solid state.
Why does the density of milk increase when cream is separated from it?
The density changes due to differences in the density between cream and milk. Cream is lighter than water and milk is heavier than water. The average density of whole milk could be close to 1.024g per liter. When the cream is removed, the density of the milk goes up to about 1.036g per liter, while the density of the cream is about 0.968g per liter.
What is the average momentum of a g6?
The average momentum of a g6 would depend on its mass and velocity. Momentum is calculated as the product of mass and velocity, so without specific values for these parameters, the average momentum cannot be determined.
Would you die if you went to a planet that had 400x stronger gravity than earth?
yes you will be crushed like a pan cake. because if for instance you weigh 20kgs and you went to a planet that had 400x stronger gravity than earth you would weigh 8000kgs and you wont even be able to move a muscle.
Special condition: if the planet were rapidly rotating then the gravity about its equator would be significantly less than that at the poles. To reduce a 400g gravity to 1g about its equator and if the planet had a equatorial radius of that of Jupiter
71 492 kilometers
399*(10m/s2) = v2/r
3990 *71492000 = v2
v= 534091m/s
T=71492000/534091 = 133 seconds
then the planet would have to have an rotational period of only 133 seconds. Not impossible for a neutron star.
What is the relative permittivity of indium arsenide?
The relative permittivity of indium arsenide (InAs) is typically around 15-17 at room temperature. This value can vary slightly depending on factors such as temperature and frequency of the electric field.
Is the lithosPhere a solid liquid or neither?
The lithosphere is a solid layer of the Earth comprising the crust and upper part of the mantle. It is neither a liquid nor a gas, but a rigid layer that rests on the more fluid asthenosphere below.
What are basis in a crystal structure of solid?
One of the basis in a crystal structure is classification of solids; classification on the basis of the symmetry of crystal structures (geometrical properties) and physical features of them.
In symmetric, we describe shape and arrangement crystals (s.c, b.c.c, f.c.c, h.c.p ,etc.) and in physical classification, decribe physical properties (The scheme is based on the configuration of the valance electrons. for example covalent crystal, ion crystal, metallic crystal and etc.)
Why is snow a crystalline solid?
yes, each snowflake is one dendritic ice crystal.
However fallen snow is not a solid, the snowflakes have stacked up to capture a larger volume of air than the volume of the snowflakes themselves.
What happens to the pressure inside a container when the temperature of a fluid is increased?
When heated, temperature increases. You may have already guessed that. Most substances, but not all, increase in volume as the temperature increases at constant pressure. The pressure would remain the same if the fluid was in an open container.
Why can iron conduct electricity?
Iron, like all metals, has electrons in its outer shell that are not tightly bound to the nucleus.
Compared to non-metals, it's easy for one or more electrons to escape from the outer shell and move freely in the metal's crystal lattice.
It's this population of free electrons that can be "recruited" and made to move in a particular direction, that makes metals good conductors.
Iron is a so-so conductor, but it's not as good as copper or silver.
Why electron does not exist in band gap?
Short Answer:
Electrons are waves and waves in a confined geometry can exist only with specific allowed wavelengths. This is true for sound waves in musical instruments, water waves in a ripple tank, light waves and electron waves in solids. Bad gaps and allowed wave regimes exist for all waves and are the consequence of simple reflection, refraction and interference.
Long Answer:
Electrons in crystals (not all solids, but only regular periodic arrays of atoms) have energies that restricted to certain allowed values or ranges of values called "bands" or "energy bands" and not other values called "gaps" or "band gaps" for a simple reason. Electrons are waves and electron dynamics is described by a wave equation, specifically the Schroeding equation. Quantum waves must respect the same dynamics as all waves and that includes the processes of reflection, refraction, and interference. It is these processes that create the bands and band gaps.
If you are asked to explain why a musical instrument gives out specific notes and not all possible sounds, you explain it as a condition of wave dynamics. A guitar string, for instance, vibrates with waves that can exist with whole wavelengths that fit within the length of the string. That is completely analogous to the phenomena that forces the existence of bands and band gaps for electrons in solids.
In fact, if you scale things up to wavelengths appropriate to sound (Sound wave are about a trillion time larger than electron waves.) you will get bands of allowed sound and band gaps where sound is not allowed. You can create a volume of space with a regular array of objects that reflect and refract sound and in that space only certain bands of wavelengths of sound will be allowed. The phenomena is the same. The equations are the same. The cause is the same.
Though quantum mechanics is strange and complicated, the reason energy bands in crystals exist is simple and completely faithful to the analogy of notes from a musical instrument.
Caveat: Though the existence of bands follows from this simple explanation, the prediction of the behavior of electrons in particular solids requires a sophisticated description of the particular atomic and electronic interactions. One can spend a career as a physicist making such descriptions and explaining the properties of the various kinds of solids.
More Answers:
Electrons may only possess specific energies. Another way of saying this is that they can only occupy certain energy levels. A band gap is a continuous spectrum of energies where no such energy levels exist. The band gap is simply a range of energies that the electron cannot have.
If you want to know why there are energies the electron can have and why there is a gap in between these energy ranges then that's quite a bit more complicated. A short answer would be that there are gaps because there are asymmetries in the basic repeating unit of the crystal structure but I appreciate that that probably prompts a bunch of other questions.
Are ferro magnetic materials insulators?
Not necessarily. Ferromagnetic materials can be conductors, semiconductors, or insulators depending on their specific composition and structure. Magnetic properties and electrical conductivity are independent characteristics of a material.
How do you derive graphene's low-energy Hamiltonian?
To derive graphene's low-energy Hamiltonian, one typically starts with the tight-binding model for graphene's honeycomb lattice. By applying the nearest neighbor approximation and using certain symmetry properties, one can simplify the model to focus on the low-energy excitations around the Dirac points in the Brillouin zone, leading to a 2x2 matrix Hamiltonian that describes the electronic properties of graphene near the Fermi level.
Electric field breaks space-inversion symmetry because it changes the sign of charges under spatial inversion. Magnetic field breaks time-reversal symmetry because reversing the direction of time changes the direction of the field's rotation or flux lines.
