When you shift your gaze from a distant tree to a book held 25 cm away, describe what happens to your ciliary…

Question

When you shift your gaze from a distant tree to a book held 25 cm away, describe what happens to your ciliary muscles and eye lens. How do these changes together bring the image of the nearby text onto the retina?

Accepted Answer

## Model Answer When shifting focus from a distant tree to a book 25 cm away, the **ciliary muscles contract**. This increases the curvature of the eye lens, making it **thicker**. As a result, the **focal length of the eye lens decreases**. A shorter focal length provides greater converging power, which is needed to focus light from the nearby book. The lens bends the incoming light rays more sharply so that they converge exactly **on the retina**, forming a clear image of the text. This adjustment is called **accommodation**. *Source: Chapter 10, Section 10.1.1 – Power of Accommodation* --- ## Explanation - Examiners expect **three linked steps**: ciliary muscles contract → lens becomes thicker/more curved → focal length decreases → image focuses on retina. - The keyword **accommodation** must appear for full marks. - Do not say focal length *increases* for nearby objects — that is the opposite (relaxed lens for distant vision). - 25 cm is the near point; mentioning it shows awarene…

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