Ch. 17 The Special Senses

Martini - Fundamentals of Anatomy and Physiology 12th Edition

Martini, Nath, Bartholomew12th EditionFundamentals of Anatomy and PhysiologyISBN: 9780137854011Not the one you use?Change textbook

Martini, Nath, Bartholomew 12th Edition

Ch. 17 The Special Senses

Problem 25

Chapter 17, Problem 25

Your friend Shelly suffers from myopia (nearsightedness). You remember from your physics class that concave lenses cause light waves to spread or diverge and that convex lenses cause light waves to converge. What type of corrective lenses would you suggest to your friend?
(a) Concave lenses
(b) Convex lenses

Verified step by step guidance

Understand the condition: Myopia, or nearsightedness, means that distant objects appear blurry because the eye focuses images in front of the retina instead of directly on it.

Recall lens behavior: Concave lenses cause light rays to diverge (spread out), while convex lenses cause light rays to converge (come together).

Analyze the problem: Since myopia causes light to focus too early (in front of the retina), the corrective lens needs to spread the light rays out slightly so they focus further back, directly on the retina.

Match the lens type: Because concave lenses cause light to diverge, they are used to correct myopia by moving the focal point back onto the retina.

Conclude the recommendation: Therefore, the appropriate corrective lenses for myopia are concave lenses.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Myopia (Nearsightedness)

Myopia is a common vision condition where distant objects appear blurry because the eye focuses images in front of the retina instead of directly on it. This occurs when the eyeball is too long or the cornea is too curved, causing light rays to converge prematurely.

Concave Lenses and Light Divergence

Concave lenses are thinner at the center and thicker at the edges, causing incoming light rays to spread out or diverge. This divergence helps move the focal point backward, which is useful for correcting myopia by adjusting where light focuses on the retina.

Convex Lenses and Light Convergence

Convex lenses are thicker at the center and thinner at the edges, causing light rays to converge or come together. They are typically used to correct hyperopia (farsightedness) by moving the focal point forward onto the retina, which is the opposite of what is needed for myopia.

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Textbook Question

Juan tells his physician that he has been feeling dizzy, especially when he closes his eyes. He is asked to stand with his feet together and arms extended forward. As long as he keeps his eyes open, he exhibits very little movement. But when he closes his eyes, his body begins to sway a great deal, and his arms tend to drift together toward the left side of his body. Why does this occur?

Textbook Question

You are at a park watching some deer 35 feet away from you. A friend taps you on the shoulder to ask a question. As you turn to look at your friend, who is standing just 2 feet away, what changes would your eyes undergo?

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Textbook Question

Damage to the ampullary cupula of the lateral semicircular duct would interfere with the perception of

(a) The direction of gravitational pull

(b) Linear acceleration

(d) Vertical rotation of the head

(e) Angular rotation of the head

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Textbook Question

Displacement of stereocilia toward the kinocilium of a hair cell

(a) Produces a depolarization of the membrane

(b) Produces a hyperpolarization of the membrane

(d) Increases the membrane permeability to potassium ions

(e) Does not affect the membrane potential of the cell