In this question, we`re considering how an air bubble in water acts according to different types of mirrors and lenses.
Option 1: Convex Mirror. This type of mirror diverges light and forms a virtual image. An air bubble doesn`t reflect light like a mirror, because it diffracts the light so it`s not a convex mirror.
Option 2: Convex Lens. This lens converges light to focus it onto a particular point. An air bubble doesn`t do this.
Option 3: Concave Mirror. This mirror converges light, but as stated before, an air bubble doesn`t act as a mirror does, because the light passes through it rather than being reflected.
Option 4: Concave Lens. This is the correct answer because a concave lens is the only one that diverges light, which is similar to how the light will spread out or diverge when it enters an air bubble in water. So, the air bubble acts like a concave lens.