a suitable power of concave lens is placed which helps to focus the light rays on retina"
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Answer:
Explanation:A concave lens is a lens that possesses at least one surface that curves inwards. It is a diverging lens, meaning that it spreads out light rays that have been refracted through it. A concave lens is thinner at its centre than at its edges, and is used to correct short-sightedness (myopia). The writings of Pliny the Elder (23–79) makes mention of what is arguably the earliest use of a corrective lens. According to Pliny, Emperor Nero was said to watch gladiatorial games using an emerald, presumably concave shaped to correct for myopia.
After light rays have passed through the lens, they appear to come from a point called the principal focus. This is the point onto which the collimated light that moves parallel to the axis of the lens is focused. The image formed by a concave lens is virtual, meaning that it will appear to be farther away than it actually is, and therefore smaller than the object itself. Curved mirrors often have this effect, which is why many (especially on cars) come with a warning: Objects in mirror are closer than they appear. The image will also be upright, meaning not inverted, as some curved reflective surfaces and lenses have been known to do.