An object is placed 30cm away from a convex lens of focal length 10cm and a sharp image is formed on a screen. Now, a convex lens is placed In contact with the convex lens. The screen now has to be moved by 45cm to get a sharp image again. The magnitude of focal length of the convex lends in (in cm)

An object is placed 30 cm away from a convex lens of focal length 10 cm and a sharp image is formed on a screen. Now a concave lens is placed in contact with the convex lens. The screen now has to be moved by 45 cm to get a sharp image again. The magnitude of focal length of the concare lens is (in cm)

An object is placed 20 cm from a convex lens of focal length 10 cm. The image must be-

An object is placed 25 cm from a convex lens whose focal length is 10 cm . The image distance is ___________ cm.

An object is placed at 12 cm from a convex lens whose focal length is 10 cm . The image must __________ .

An object is placed at 10 cm from a convex lens of focal length 12 cm. Find the position, nature and magnification of the image.