A lens is a transmissive optical device that disperses or focuses a light ray by means of refraction. Concave means hollowed inward or curving in; so, concave lenses are hollowed inward. A concave lens is also called as a negative lens or a diverging lens. There are numerous uses of the concave lens, like in telescopes, cameras, lasers, glasses, binoculars, etc.
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Concave Lens Uses
A concave lens has at least one surface which is curved inwards, relative to the plane of the surface. The middle part of a concave lens is a lot thinner than the edges of the lens. When light rays fall, on a concave lens, the light rays bend outwards and diverge away from each other. The image formed upright and smaller than the actual object. Some interesting and common concave lens uses are given in the points below.
Concave lens used in glasses
Concave lenses are most commonly used to correct myopia which is also called near-sightedness. The eyeball of a person who has myopia is too long, and the images of faraway objects fall short of the retina. Therefore, concave lenses are used in glasses which correct the shortfall by spreading out the light rays before it reaches the eyeball. This enables the person to see far-away objects more clearly.
Uses of concave lens in lasers
Different types of scanners, medical equipment, and CD and DVD players use laser beams. As the laser beams are highly focused, they are dispersed so that the equipment works properly. Small concave lenses are used which widen the laser beam to sharply access a specific area.
Use of concave lens in cameras
To improve the quality of photographs, combinations of convex and concave lenses are widely used by camera manufacturers. When only a convex lens is used as the primary lens of a camera, it causes distortions in the photos, which are called chromatic aberrations. Combining both concave and convex lenses eliminated the undesirable effects.
Used in flashlights
Concave lenses are also used in flashlights to magnify the light produced by the source. The light rays fall on the hollowed side of the lens, and the light rays diverge on the other side. This increases the radius of the light source and thus provides a wider beam.
Concave lens used in peepholes
Peepholes or door viewers are security devices that give a panoramic view of objects outside walls or doors. A concave lens is used to minimise the proportions of the objects and gives a wider view of the object or area.
Previous year questions in the chapter Light: Reflection and Refraction
Theory and important questions of the chapter Light: Reflection and Refraction
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