Answer:
CONVEX LENS
The convex lens is a lens that converges rays of light that convey parallel to its principal axis (i.e. converges the incident rays towards the principal axis) which is relatively thick across the middle and thin at the lower and upper edges. The edges are curved outward rather than inward.
A convex lens is thicker in the middle than at the edges. You can see the shape of a convex lens in the Figure below. A convex lens causes rays of light to converge, or meet, at a point called the focus (F). A convex lens forms either a real or virtual image.
Convex (converging) lenses can form either real or virtual images (cases 1 and 2, respectively), whereas concave (diverging) lenses can form only virtual images (always case 3). Real images are always inverted, but they can be either larger or smaller than the object.
Convex lenses are used in eyeglasses for correcting farsightedness, where the distance between the eye's lens and retina is too short, as a result of which the focal point lies behind the retina. Eyeglasses with convex lenses increase refraction, and accordingly reduce the focal length.
The structure of convex lens is like, thicker at the centre and thinner at the edges. Conversely, the concave lenses are thinner at the centre and thicker at its edges, in structure. The focal length of a convex lens is positive, while that of a concave lens is negative.
CONCAVE LENS
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 shape of a concave lense is round inward that bends the beams outward, causing divergence of the rays of light falling on it, so it is known as a diverging lens. This also makes the object look smaller and farther than they really are and the image formed is virtual, diminished and upright.
The image formed is virtual as we see that the light appears to pass through the focus behind the lens. ... Hence, the image formed by a concave lens is always erect and virtual.
A concave lens is used to diverge incident rays. This helps to create a virtual image on the opposite side of the refracting surface. Hence, these lenses are used in binoculars, telescopes, cameras, flashlights and eyeglasses.
Concave lenses represent the type of lenses which are slender at the centre than at the borders. The shape of a concave lense is round inward that bends the beams outward, causing divergence of the rays of light falling on it, so it is known as a diverging lens.
