Which of the following causes objects to appear larger and closer when looking through a mask during a dive?

Looking through a scuba mask makes objects appear larger and closer primarily due to refraction. Refraction occurs when light passes from one medium to another, in this case, from water into the air space within the mask. The change in medium alters the speed and direction of the light rays, causing them to bend. This bending of light creates an optical illusion that magnifies and brings objects into clearer focus, making them seem larger and closer than they actually are.

In contrast, the other options involve different physical phenomena that do not contribute to the magnification effect experienced through a mask. For instance, reflection pertains to the bouncing back of light from surfaces, which does not create the illusion of proximity or size increase in this context. Diffraction involves the bending of light around obstacles or through openings, but it does not enhance the appearance of objects as seen through the mask. Absorption deals with the soaking up of light by materials, which again does not aid in magnifying or bringing objects closer. Thus, refraction is the key mechanism at play when experiencing objects through a scuba mask.