How the eye focuses light

你需要知道的

• Light is refracted first by the cornea and then again by the lens so that it focuses on the retina.
• The image on the retina is upside down, and the brain interprets it the right way up.
• In short-sightedness the eye is too long, so light focuses in front of the retina and distant objects look blurred; a concave lens corrects it.
• In long-sightedness the eye is too short, so light focuses behind the retina and near objects look blurred; a convex lens corrects it.

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