magnification

an object is placed in front of a lens. the table below shows the information of different cases. for each case find the magnification and the nature of the image
唔用graph點找(用唔到height of image/height of object and image distance/object distance )


lens type ______ focal length______ object distance
a)convex______ 10 _______15

b)convex ______ 10 _______ 30

c)convex ______ 20 ______ 20

D)convex _______ 20 ________ 40

e)convex _______ 30 _______ 15

f)concave _______ 20 _______ 15

g)concave _______ 20 ______ 20

h)concave _______ 10 ______ 30