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Architectural Acoustics
Published in Malcolm J. Crocker, A. John Price, Noise and Noise Control, 2018
Malcolm J. Crocker, A. John Price
If the reflecting surface is not a plane, but curved, then the rays will be focused in a similar manner to that found in optics for reflection by curved mirrors. In the case of a concave reflecting surface, sound rays will be focused to a point forming a real acoustic image. This can be most undesirable acoustically, since it will result in a "hot spot" within the room which will be very loud while it would be considerably quieter at other points away from the focus in the room. Figure 5.4 shows that the image produced by a concave reflector can be located by using the fact that rays traveling parallel to the axis will be reflected through the focus (equal to one half of the radius of curvature R) and conversely, rays travelling through the focus will be reflected parallel to the axis. Again, in order for this focusing effect to take place the dimensions of the concave surface must be larger than a wavelength (see Equation 1.27) and the surface must be smooth and reflective. This effect must be avoided in architectural acoustics since it leads to hot spots and echoes. Many auditoria have concave rear walls or balconies with concave front walls which would give rise to echoes at the front of the audience or even on the stage if not properly treated to be made highly absorbent. Domes and shell ceilings can cause similar effects and almost always result in an acoustic problem.
Optics and optical instruments
Published in Andrew Norton, Dynamic Fields and Waves, 2019
In the previous section, you saw how rays parallel to the optical axis of a lens or curved mirror converge on — or appear to diverge from — a point on the optical axis known as the focal point. But in imaging systems we are often not so much interested in what the lens or mirror does to parallel rays, but in what it does to rays diverging from an object. A first step in investigating this question further is to initially restrict the argument to point-source objects on the axis, and then extend the discussion to include off-axis point objects, and extended objects.
Understanding Optics
Published in Barat Ken, Laser Safety Tools and Training, 2017
Mirrors with curved surfaces are also common in laser technology. Just as with lenses, because the rays from a plane wave strike various points on a curved mirror at different incidence angles, the rays can be brought to a focus for a concave mirror or diverge from a virtual focus for a convex mirror.
Review on advancement in solar and waste heat based thermoelectric generator
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Sanjeev Kumar Bhukesh, Suresh Kumar Gawre, Anil Kumar
Solar furnace is designed to produce high temperature by capturing sunlight and applying industries through a curved mirror that works as a parabolic reflector. The curved mirror concentrates the light over a focal length. Focal length can reach up to 6330F (i.e. 3500°C) and generated heat can produce nanomaterial, hydrogen fuel, melting steel and electricity generation. To attain high temperatures, solar energy is concentrated inside the solar furnace. It constitutes heliostats or parabolic mirrors for concentrating light over a focal length. It has a mechanical structure and complex optical structure with a system that is controlled automatically. Solar furnace principle is applied to solar water pasteurization, solar powered barbecues, and low-cost solar cookers.