A lens of power `+2` dioptres is placed in contact with a lens of power `-1` dioptre. The combination will behave like

A lens of power +3.5 diopters is placed in contact with a lens of power -2.5 diopter. The combination will behave like :

A lens of power +3.5D is placed in contact with a lens of power -2.5 D. The combination will behave like

A lens of power 6 D is put in contact with a lens of power -4 D. The combination will behave like a

a convex lens of power +6 dioptre is placed in contact with a concave lens of power -4 dioptre. What will be the nature and focal length of this combination?

a convex lens of power +6 dioptre is placed in contact with a concave lens of power -4 dioptre. What will be the nature and focal length of this combination?

Two lenses of power +12 and -2 dioptres are placed in contact. The combined focal length of the combination will be

Two lenses of power +12 and -2 dioptres are placed in contact. The combined focal length of the combination will be

A convex lens of power +5 D is placed in contact with a concave lens of power -4 D. What is the power of combination and nature of lens combination ?

Two lenses of power 15 and - 3 dioptre are placed in contact. The focal length of the combination is