Photoreceptor cells are found only in the "retina" of the eye and house the rods and cones, which break down in the presence of light. This allows the transduction of light energy into electrical energy within the nervous system, which is channeled back to the visual centers of the brain for processing.

The other choices are incorrect. The "lens" is responsible for focusing light onto the retina and the photoreceptor cells that comprise it. The "ciliary muscles" control the shape of the lens when focusing on objects, while the "sclera" is the hard, white, outer surface of the eye. Neither of these areas contain photoreceptors.

The frequency of a sound-wave determines its perceived pitch. Pitch could be described as the musical note which would correlate with the particular tone. The amplitude of a sound-wave, on the other hand, determines its loudness. High frequency sound-waves produce higher pitched notes than lower frequency waves, while high amplitude sound-waves will produce louder sounds than lower amplitude waves.

Timbre is a complex quality of sound better described as its particular "voice" and is the reason why an A flat or a C sharp on a piano sounds different from the same note played on a trumpet. Timbre is not the result of individual frequencies or amplitude, but rather the combination of other factors.

A big part of the way humans learn is by starting with a very general concept, and then organizing more detailed concepts within that general paradigm. This means that concepts we have learned before can influence new ideas and concepts that we are learning. When reading a sign, you use your previous knowledge of possible words and phrases, and put that together with the sensory knowledge you acquire from the sign.

Gestalt's principles do reference the phenomena of the mind making a whole based on small parts, but generally refers to visual construction as opposed to semantic meaning. 

Prosopagnosia can be either congenital or acquired. Congenital cases are more rare, and the most difficult to treat. Acquired prosopagnosia usually results from damage to the occipito-temporal lobe. The fusiform gyrus has been shown to activate in response to faces in several different neuro-psychological studies. This disorder is famously chronicled in the novel "The Man Who Mistook His Wife for a Hat" by Oliver Sacks.

Our brains use the differences in the location of an object on our retinas in order to judge their relative distance from one another. This requires two eyes, and thus is binocular. The other cues listed require only one eye (monocular).

Gate-control theory posits that the spinal cord contains a "gate" that controls whether pain signals get sent to the brain or not. This "gate" is opened based on the strength of the pain signals from the body. 

Figure-ground is a perception used to distinguish a figure from its background, whether that be black words on a white page or distinguishing a particular voice from a crowd. There are many cues that enable us to distinguish a figure from its background, like color, shapes, edges, movements, or sounds. Figure-ground perception is a part of “Gestalt principles," or the prcoess of evaluating the bigger picture.   

Justin can physically speak, so we can rule out Broca's area, which is in the frontal lobe. However, he is unable to understand language, which is handled by Wernicke’s area. Wernicke’s area is located in the temporal lobe.

Retinal disparity is a binocular cue that involves observing the difference between the two images the retinas receive of a single object. The greater the difference, the closer the object is to the viewer.

The retina captures external light and converts it into visual images that are sent to the brain. The retina contains rods, which detect black and white, and cones, which detect color.