A concave lens is also called a diverging or negative lens and has at least one surface that curves inward like a spoon or cave. When light falls on a concave lens, the rays deviate outward and diverge away from each other. The middle of a concave lens is thinner than the edges, and the image created is upright but smaller than the original object. Concave lenses are used in a variety of technical and scientific products.
Binoculars and Telescopes
The main purpose of binoculars and telescopes is to magnify objects, using convex lenses as a primary source. However, convex lenses do not transfer light accurately, giving way to distortions and blurs. Binocular and telescope manufacturer's therefore install concave lenses in either the eye or objective pieces to help focus images more clearly for the viewer's eyes.
Opticians use concave lenses to correct nearsightedness, also called myopia. Nearsightedness is a condition where the eye is too long, and the image falls short of the retina when the object looked at is far away. Concave lenses in glasses correct the shortfall by spreading out the light before it reaches the eye, thereby enabling the viewer to see distant objects clearly.
Camera manufacturers use combinations of concave and convex lenses to improve the quality of photographs. The primary lens of a camera is convex, which, when used alone, can cause distortions called chromatic aberration in the photographs. Convex lenses focus light of different colours in different places, which creates a fringe effect around bright objects in the picture. This can be avoided by combining convex lens and concave lenses.
Concave lenses are used on flashlights to increase the beam of the light source. Light from a bulb falls on the concave side of the lens, which diverges the rays on the other side, thereby increasing the radius of the light source and providing a wide beam.
Medical equipment, scanners and CD players use laser beams that are modified with the help of small concave lenses in order to operate to specifications. The concave lenses expand the ratio of the laser beam to precisely access a specific area. Concave lenses used with lasers are made from fused silica to withstand the ultraviolet rays produced by the light source.
Door viewers, or peepholes, are small security devices that provide a panoramic view of objects and environments outside doors or walls. The view is created through the use of one or more concave lenses inside the device which minimises the proportions of specific objects and gives a wide overview of an entire area.