Archaeology laser (light amplification by stimulated emission of radiation) to transmit a light pulse and a receiver with sensitive detectors to measure the backscattered or reflected light. Distance to the object is determined by recording the time between the transmitted and backscattered pulses and using the speed of light to calculate the distance travelled. Lidars can determine atmospheric profiles of aerosols, clouds, and other constituents of the atmosphere. Laser altimeter A laser altimeter uses a lidar (see above) to measure the height of the instrument platform above the surface. By independently knowing the height of the platform with respect to the
Sound amplification by stimulated emission of radiation of semiconductors that together form quantum wells. In these wells, electrons can be excited by parcels of ultrasound of millielectronvolts of energy. This amount of energy is equivalent to a frequency of 0.1 to 1 THz. Just as light is a wave motion that is considered as composed of particles called photons, we can think of the normal modes of vibration in a solid as being particle-like. The quantum of lattice vibration is called phonon. In lattice dynamics we want to find the normal modes of vibration of a crystal. In other words, we need to calculate the energies (or