The correct answer is -6 D.![image](//cdn. Points

• The power of a lens is defined as the reciprocal of its focal length in meters: P = 1/f (in meters).

• When two lenses are placed in contact with each other, their resultant power is the algebraic sum of their individual powers: P(resultant) = P1 + P2.

• Here, the power of the convex lens (P1) is +4 D, and the power of the concave lens (P2) is -10 D.

• Resultant power = +4 D + (-10 D) = -6 D.

• A negative power indicates that the combined system behaves as a concave lens, which is diverging in nature.![image](//cdn. Information**

• Convex Lens (+4 D):

• A convex lens is a converging lens that brings parallel rays of light to a focus.

• Its power is positive, indicating that it produces a real and inverted image if the object is placed beyond the focal point.

• In this case, the convex lens has a power of +4 D, which corresponds to a focal length of 0.25 m (f = 1/P).

• Concave Lens (-10 D):

• A concave lens is a diverging lens that causes parallel rays of light to spread out as if they were emanating from a virtual focal point.

• Its power is negative, indicating that it produces a virtual and upright image.

• In this case, the concave lens has a power of -10 D, which corresponds to a focal length of -0.1 m (f = 1/P).

• Resultant Lens Behavior:

• The resultant power of the lens system is -6 D, meaning the system behaves like a concave lens with a focal length of -0.1667 m.

• This combined lens system would diverge light rays, as indicated by the negative resultant power.