A convex lens is used to obtain a magnified image of an object on a screen 10 m from the lens .If the magnification is 19,find the foal length of the lens.

Show that a convex lens produces an N times magnified image,when the object distances from the lens have magnitude (f+- f//N) .Here,f is the magnitude of the focal length of the lens.Hene,find the two values of object distance,for which a convex lens of power 2.5 D will produce an image that is four times as large as the object.

If the distance between the screen and object is 50 cm and the displacement of the lens is 10 cm,clculate the focal length of the lens.

An object is placed at a distance of 1.5 m from a screen and a convex lens is interosed between them .the magnification produced is 4.What is the focal length of the lens?

A concave lens has focal length of 15 cm. At what distance should the object from the lens be placed so that it forms an image at 10 cm from the lens? Also find the magnification produced by the lens.

A screen is placed 90cm from an object. The image of the object on the screen is formed by a convex lens at two different locations separated by 20cm. Determine the focal length of the lens.

A convergeing lens is used to form an image on a screen.When the upper half of the lens is converd by an opaque screen,

Draw a ray diagram to show how the image is formed when the object is placed between f and 2 f distances from a convex lens.Deduce the relation between the distances of he oject and the image from the lens and the focal length of the lens under this condition.

A double convex lens has 10 cm and 15 cm as its two radii of curvature.The image of an object,placed 30 cm from the lens,is formed at 20 cm from the lens on the other side.Find the refractive index of the material of the lens.Whgat will be the focal length ?What will be the focal length of the lens,if it is immersed in water of refractive index 1.33?

A convex lens from a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle be placed in front of the convex lens if the image is equal to size of the object? Also, find the power of the lens?