The visual unit of compound eye of Cockroach is

The correct answer is Ommatidium

Explanation:

• The compound eye is a characteristic feature of arthropods, including cockroaches. It consists of multiple small visual units called ommatidia, each functioning as an independent photoreceptor.
• In cockroach, the sense organs are antennae, eyes, maxillary palps, labial palps, anal cerci, etc.
• The compound eyes are situated at the dorsal surface of the head.
• Each eye consists of about 2000 hexagonal ommatidia (sing.: ommatidium).
• With the help of several ommatidia, a cockroach can receive several images of an object.
• This kind of vision is known as mosaic vision with more sensitivity but less resolution, being common during night (hence called nocturnal vision).

Other Options:

• Cornea: The cornea is the outermost transparent structure of each ommatidium in the compound eye.
• Retina: The retina is a part of the vertebrate eye, not the compound eye of insects like cockroaches. In the compound eye, the retinula (a group of photoreceptor cells) is the functional equivalent of the retina.
• Cones: The crystalline cone is a part of the ommatidium that helps focus light onto the photoreceptor cells. However, cones themselves are not visual units but rather components within the ommatidium.