The part of human eye which controls the amount of light entering into it is:
Step 1: Identifying the structure. The iris is the part of the human eye that controls the size of the pupil and, in turn, regulates the amount of light entering the eye.
Step 2: Conclusion. Thus, the correct answer is option (A): Iris.

A symmetric thin biconvex lens is cut into four equal parts by two planes AB and CD as shown in the figure. If the power of the original lens is 4D, then the power of a part of the divided lens is:

आपका घनिष्ठ मित्र दूसरे मुसीबत को, आपके घर में उसका स्वागत किस प्रकार करता है? विस्तार से लिखिए।