The image of the needle placed 10 cm from a lens is formed on a wall 20 cm on the other side of the lens. Find the focal length of the lens and size of the image formed if the size of the needle is 2.5 cm.

The image of needle placed 45 cm from a lens is formed on a screen placed 90 cm on the otehr side of teh lens.Find the displacement of the image,if the object is moved to 5.0 cm away from the lens.

A needle placed 40 cm from a lens forms an image on a screen placed 80 cm on the other side of the lens. Identify the type of lens and determine its focal length. What is the size of the image, if the size of needle is 15 cm ?

A needle placed 45cm from a lens forms an image on the screen placed 90cm on the other side of the lens. What is the type of lens ? Find the focal length. If the length of needle is 5cm. What is the length of image ?

An object is 2m away from a lens. Which forms an erect image 1/4th the size of the object, determine the focal length of the lens.What type of the lens is this?

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?

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.

The image obtained with a convex lens is erect and its lenth is four times the length of the object.If the focal length of the lens is 20 cm,calculate the object and image distance.