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Do You Know
Questions & Answers on General Knowledge.

Question:
Does your pupil opening and closing have anything to do with it focusing on a more distant object?
Answer:
The size of your pupil does not depend on the distance to an object. It depends only on how bright the scene in front of you is. But the size of your pupil does affect your ability to focus. When it is relatively dark and your pupil is wide open, the whole lens of your eye is involved in light gathering. Focusing becomes very critical and you have very little depth of focus. Moreover, if your lens isn't perfect, you will see things as blurry. But when it is bright out and your pupil is small, you are only using the center portion of your lens and everything is in focus. That's why it is harder to focus at night than during the day. When you squint, you are artificially shrinking the effective diameter of the lens in your eye and increasing your depth of focus. Unfortunately, you are also reducing the amount of light that reaches your eye. If you look through a pinhole in a sheet of paper, you will find everything in focus, although it will appear very dim.
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    Snow White Penguin Chick

    Not all emperor penguins sport black and white tuxedoes. Scripps reseacher Gerald Kooyman spotted this unique all white emperor chick, dubbed Snowflake, during a penguin survey on the ice shelf of the Ross Sea, Antarctica, in December 1997. Its white feathers blended in so well with the icy background that Kooyman said he almost missed the chick emperor penguin chicks are usually covered in a grayish down coat, with dark tail feathers and dark bills and feet. Scientists dont think Snowflake is an albino, however, as it didnt have the characteristic pink eyes associated with albinism.


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