Physics Ghost fish Air Water 削荆 PHYSICS Normal PHUN Air Water < 6
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Types of spherical lenses: biconvex Plano-convex convex meniscus Biconcave Plano-concave concave meniscus The formation of these lenses may be understood from the figures below... B1王 Biconvex Plano- Comvex- Meniscus Plano- Biconcave convex concave concave 7
Types of spherical lenses: biconvex Plano-convex convex meniscus Biconcave Plano-concave concave meniscus The formation of these lenses may be understood from the figures below… 7
Images formed by convex lenses If the incident rays are parallel(that is come from infinity),they will be converged upon a single point on the other side of the lens;at this point the image will be formed...This point is known as the principal focus,and its distance from the lens is called the focal length. Fig.The incident rays are parallel,coming from infinity;the focus (F)is called the principal focus. In practice,an object which is 6 meters or more away,is considered to be at infinity,and the rays of light issuing from it are parallel 8
Images formed by convex lenses If the incident rays are parallel (that is come from infinity), they will be converged upon a single point on the other side of the lens; at this point the image will be formed… This point is known as the principal focus, and its distance from the lens is called the focal length. 8 Fig. The incident rays are parallel, coming from infinity; the focus (F) is called the principal focus. In practice, an object which is 6 meters or more away, is considered to be at infinity, and the rays of light issuing from it are parallel
Images formed by concave lenses The construction of images formed by concave lenses. These lenses diverge the rays of light so that they never form a real image but always a virtual one. When the object is in any position, it will be found that the image is virtual,erect,and smaller than the object Fig.The image formed by a concave lens.If AB is the object,the image ab is diminished and erect and, being formed on the same side of the lens as that from which the incident light comes,is virtual. 9
Images formed by concave lenses • The construction of images formed by concave lenses. • These lenses diverge the rays of light so that they never form a real image but always a virtual one. • When the object is in any position, it will be found that the image is virtual, erect, and smaller than the object • Fig. The image formed by a concave lens. If AB is the object, the image ab is diminished and erect and, being formed on the same side of the lens as that from which the incident light comes, is virtual. 9
Fig.The measurement of the strength of lenses.A straight line is viewed through the lens and the latter is moved in the direction of the arrow.In the case of a concave lens(A)the line appears to be displaced in the direction of movement.In a convex lens(B)the line appears to be displaced in the opposite direction. 10
10 Fig. The measurement of the strength of lenses. A straight line is viewed through the lens and the latter is moved in the direction of the arrow. In the case of a concave lens (A) the line appears to be displaced in the direction of movement. In a convex lens (B) the line appears to be displaced in the opposite direction