Write short notes on1. Apposition image2. Superposition image

1.	Write short notes on1. Apposition image2. Superposition image
Answer» 1. Apposition image : It is formed during moderate to bright light. It is also called as mosiac image. The pigmented sheaths expand to make die ommatidium optically isolated in the bright light. The image of one part of the object is formed in one ommatidium. Hence, it is a distinct image. In cockroach, only mosiac vision is formed. 2. Superposition image : It is formed in dim-light & in the night. There is contraction of the pigmented sheat. Hence the optical isolation is lost. It is an indistinct image. The image of one part of the object is formed in many adjacent ommatidia.

Answer»

1. Apposition image :

It is formed during moderate to bright light. It is also called as mosiac image.
The pigmented sheaths expand to make die ommatidium optically isolated in the bright light. The image of one part of the object is formed in one ommatidium. Hence, it is a distinct image. In cockroach, only mosiac vision is formed.

2. Superposition image :

It is formed in dim-light & in the night. There is contraction of the pigmented sheat. Hence the optical isolation is lost. It is an indistinct image. The image of one part of the object is formed in many adjacent ommatidia.

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