Search results
Results from the WOW.Com Content Network
Active acoustic location involves the creation of sound in order to produce an echo, which is then analyzed to determine the location of the object in question. Passive acoustic location involves the detection of sound or vibration created by the object being detected, which is then analyzed to determine the location of the object in question.
An electromagnetic acoustic transducer (EMAT) is a transducer for non-contact acoustic wave generation and reception in conducting materials. Its effect is based on electromagnetic mechanisms, which do not need direct coupling with the surface of the material. Due to this couplant-free feature, EMATs are particularly useful in harsh, i.e., hot ...
An acoustic wave is a mechanical wave that transmits energy through the movements of atoms and molecules. Acoustic waves transmit through fluids in a longitudinal manner (movement of particles are parallel to the direction of propagation of the wave); in contrast to electromagnetic waves that transmit in transverse manner (movement of particles at a right angle to the direction of propagation ...
In semiconductors, the band gap of a semiconductor can be of two basic types, a direct band gap or an indirect band gap. The minimal-energy state in the conduction band and the maximal-energy state in the valence band are each characterized by a certain crystal momentum (k-vector) in the Brillouin zone. If the k-vectors are different, the ...
When the incident light beam is at Bragg angle, a diffraction pattern emerges where an order of diffracted beam occurs at each angle θ that satisfies: [3] = Here, m = ..., −2, −1, 0, +1, +2, ... is the order of diffraction, λ is the wavelength of light in vacuum, and Λ is the wavelength of the sound. [4]
A similar procedure is adopted to determine the optical bandgap of crystalline semiconductors. [5] In this case, however, the ordinate is given by (α) 1/r, in which the exponent 1/r denotes the nature of the transition: [6], [7], [8] r = 1/2 for direct allowed transitions; r = 3/2 for direct forbidden transitions. r = 2 for indirect allowed ...
Echo sounding or depth sounding is the use of sonar for ranging, normally to determine the depth of water . It involves transmitting acoustic waves into water and recording the time interval between emission and return of a pulse; the resulting time of flight , along with knowledge of the speed of sound in water, allows determining the distance ...
In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to the energy difference (often expressed in electronvolts ) between the top of the valence band and the ...