A convex lens in a medium with index larger than that of the lens will act like a divergent lens, yes. If you consider the focal length positive or negative will depend on the convention used. So f is positive for a convex lens and negative for a concave lens. why is the focal length of a convex lens is taken positive and that of a concave lens as negative - Physics - TopperLearning.com | 1j4w9l77 A spherical mirror and a spherical lens each have a focal length of -10 cm. The polarity of the focal length is negative in the case of the concave lens while it is positive for a convex lens. On the contrary, the image formed by the concave lens is erect, virtual and smaller, than the object. focal length. positive, if on the same side as object (real) negative, if on the opposite side as object (virtual) convex mirror. The focal length, is positive for a concave mirror, and negative for a convex mirror. image distance. Focal length (f) is positive for a convex lens and convex mirror. Generally, a convex lens forms a real image, but it can also create a virtual image when the object is in the middle of the focus and optical centre. The focal length of the convex mirror is positive, whereas that of the concave mirror is negative. Using the terminology of diverging and converging is not appropriate nor useful for mirrors. The same can also be proved by using the mirror formula: (1/f = … Focal length of a concave mirror is (a) negative (b) positive (c) depends on the position of object (d) depends on the position of image ... (c) -50 cm (d) +100 cm . However, in the convex lens, the edges are comparatively thinner than the center of the lens. The same optic laws apply to negative lenses as they do with positive lenses, but a negative lens works in a somewhat different way than a positive lens. Focal length is negative for concave lens and concave mirror. By usual convention, the focal lens of divergent lenses is taken with minus sign. object distance. negative,as all images are virtual and on the opposite side as object (virtual) concave mirror. Whether focal length of concave mirror will be positive or negative depends on the convention that you are using. Principal focus of a convex lens is the point on the principal axis of the convex lens where light rays travelling parallel to the principal axis meet after getting refracted from the lens. Answer Answer: c Question 8. So the image distance is positive here. The focal length of a convex lens is positive, while that of a concave lens is negative. A concave lens exhibits a cave-like structure from the outside as it has a thinner middle portion and thick edges. This is the physical fact. As a result, the focal length is positive for converging/concave mirrors and negative for … negative. positive. Image distance (v) can be both positive and negative for convex lens and concave mirror depending on the position of the object. The focal length is positive for 'real focal points'--meaning light *actually* converges at the focal point, and is negative for 'virtual focal points'--light only *appears* to converge at a focal point. you can easily verify that the focal length is in the positive x direction for a convex lens while it is along the negative x direction for a concave lens. Image distance is always negative for a concave lens. When the image distance is positive, the image is on the same side … Concave mirror forms real images for certain object distances whereas convex mirror does not form real image for any object distance. positive. positive. The focal length positive or negative is determined on the basis of sign conventions and definition of principal focus. By obtaining the Real image of a distant object at its focus, the focal length of the concave mirror can be estimated as shown in the diagram. The focal lengths of this type of lens are negative, this can be worked out mathematically by assigning a negative radii of curvature to a concave lens surface. Hence the rays converge to a single point infront of the lens.

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