Which part of the eye reacts to light and transmits signals to the brain?

The retina is the correct answer because it is the part of the eye responsible for detecting light and converting it into electrical signals that are sent to the brain. It contains photoreceptors known as rods and cones, which respond to varying levels of light and different wavelengths, allowing us to perceive images and colors. Once the light hits the retina, the information is processed and transmitted via the optic nerve to the brain, where it is interpreted as vision.

The macula, while important for central vision and visual acuity, does not play a direct role in reacting to light. Instead, it is a small area within the retina that contains a high concentration of photoreceptor cells. The pupil is the opening that regulates the amount of light entering the eye but does not convert light into signals. The lens focuses light onto the retina but also does not have a role in detecting light itself. Thus, the retina stands out as the key component responsible for light detection and signal transmission to the brain.