Guyton and Hall Physiology Chapter 50 - The Eye I. (Optics of Vision)
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Questions and Answers

What is the characteristic of a cylindrical lens with a strength of +1 diopter?

  • It focuses parallel light rays to a line focus. (correct)
  • It diverges light rays.
  • It forms an image on both sides of the lens.
  • It has a focal point at infinity.

    • What effect do diverging light rays have on the focal length of a concave lens?

  • They have no effect on the focal length.
  • They lengthen the focal length.
  • They create a virtual focal point behind the lens. (correct)
  • They shorten the focal length.

    • If the axis of a cylindrical lens is vertical, what is its orientation in degrees?

  • 90 degrees (correct)
  • 180 degrees
  • 45 degrees
  • 0 degrees

    • What does a stronger lens imply about the location of its focal point?

    <p>The focal point is nearer to the lens.</p> Signup and view all the answers

    What is a key difference between convex and concave lenses?

    <p>Convex lenses always converge light; concave lenses diverge it.</p> Signup and view all the answers

    What happens when parallel rays enter a convex lens?

    <p>They focus at one point beyond the lens.</p> Signup and view all the answers

    How can a convex lens focus diverging rays?

    <p>By changing its curvature.</p> Signup and view all the answers

    What is the role of the center of a convex lens in image formation?

    <p>It does not refract light and allows rays to pass straight through.</p> Signup and view all the answers

    Which characteristic differentiates a convex lens from a concave lens?

    <p>Convex lenses focus light inward, while concave lenses disperse it.</p> Signup and view all the answers

    If an object is placed in front of a convex lens, the resulting image is a mosaic of point sources. What does this mean?

    <p>Each point source of light forms a distinct point focus at varying brightness.</p> Signup and view all the answers

    How does the curvature of a convex lens affect its focal length?

    <p>A more curved lens has a shorter focal length.</p> Signup and view all the answers

    What occurs to light rays generated by point sources when they pass through a convex lens?

    <p>They converge at one point along the axis.</p> Signup and view all the answers

    Which of the following statements is true regarding the function of a convex lens?

    <p>It can focus both parallel rays and diverging rays at the same distance.</p> Signup and view all the answers

    What happens to parallel light rays passing through a concave lens?

    <p>They diverge after passing through the lens.</p> Signup and view all the answers

    How does a convex cylindrical lens differ from a concave lens?

    <p>A convex cylindrical lens bends light rays in only one plane.</p> Signup and view all the answers

    What is the primary function of a convex lens?

    <p>To bend light rays to a single focal point.</p> Signup and view all the answers

    In which scenario do parallel light rays maintain their path when passing through a lens?

    <p>When hitting the lens's center perpendicularly.</p> Signup and view all the answers

    What is the result of using two crossed cylindrical lenses?

    <p>They combine to function like one spherical lens.</p> Signup and view all the answers

    What defines the focal point for a lens?

    <p>The point where parallel rays converge.</p> Signup and view all the answers

    What is the behavior of light rays at the edges of a concave lens?

    <p>They curve outward, causing divergence.</p> Signup and view all the answers

    Which statement is true regarding the behavior of a convex lens?

    <p>It bends light rays towards a single focal point.</p> Signup and view all the answers

    How does the curvature of a lens affect light rays?

    <p>Correct curvature converges rays to a single point.</p> Signup and view all the answers

    What characteristic distinguishes a concave lens from a convex lens?

    <p>Concave lenses can create virtual images.</p> Signup and view all the answers

    What is the distance known as where parallel rays converge to a common point when passing through a convex lens?

    <p>Focal length</p> Signup and view all the answers

    When light rays that are diverging enter a convex lens, how does their focal point relate to the lens compared to parallel rays?

    <p>It is farther from the lens than that of parallel rays.</p> Signup and view all the answers

    What type of lens converges light rays in one plane?

    <p>Convex cylindrical lens</p> Signup and view all the answers

    In the context of lens optics, what is a characteristic of concave cylindrical lenses?

    <p>They diverge light rays in only one plane.</p> Signup and view all the answers

    Which statement describes the behavior of light rays when using a cylindrical lens?

    <p>They can create additional focal lines for diverging rays.</p> Signup and view all the answers

    What happens when a cylindrical lens is used to focus light from a point source?

    <p>It focuses the rays into a line focus.</p> Signup and view all the answers

    Which lens type causes light rays to diverge?

    <p>Concave lens</p> Signup and view all the answers

    Which lens would be used to demonstrate the focusing of parallel light rays in a simple experiment?

    <p>Convex lens</p> Signup and view all the answers

    What characterizes the focal distance for light sources that are not far away when using a convex lens?

    <p>The distance is shorter than for parallel rays.</p> Signup and view all the answers

    What is the result of using two cylindrical lenses at right angles to each other?

    <p>They create the equivalent effect of a spherical lens.</p> Signup and view all the answers

    What is the refractive power of a lens that converges parallel light rays to a focal point 10 centimeters beyond the lens?

    <p>+10 diopters</p> Signup and view all the answers

    Which statement describes the refractive power of concave lenses?

    <p>Concave lenses cannot be measured by focal distance beyond the lens.</p> Signup and view all the answers

    If a concave lens diverges light rays as much as a +10-diopter lens converges them, what is its dioptric strength?

    <p>-10 diopters</p> Signup and view all the answers

    What results from placing a 1-diopter concave lens immediately in front of a 1-diopter convex lens?

    <p>A lens system with zero refractive power</p> Signup and view all the answers

    How is the strength of cylindrical lenses computed in comparison to spherical lenses?

    <p>Cylindrical lenses require stating the axis along with strength.</p> Signup and view all the answers

    What happens to light rays when they pass through a convex lens?

    <p>They converge to a point.</p> Signup and view all the answers

    What is the dioptric strength of a concave lens that diverges light rays at the same rate as a 1-diopter convex lens converges them?

    <p>-1 diopter</p> Signup and view all the answers

    In which scenario would the refractive power of a lens be considered neutral?

    <p>A concave lens placed in front of a convex lens of equal strength.</p> Signup and view all the answers

    What is the effect of placing a +10 diopter lens in combination with a -10 diopter lens?

    <p>They produce a neutral effect.</p> Signup and view all the answers

    If a concave lens has a strength of -5 diopters, how does it affect incoming parallel light rays?

    <p>They diverge from a point.</p> Signup and view all the answers

    What is the significance of light rays passing through the center of a convex lens?

    <p>They do not change direction.</p> Signup and view all the answers

    How do variations in the convexity of a lens affect the focusing of light rays?

    <p>It allows both parallel and diverging rays to focus at the same distance.</p> Signup and view all the answers

    What happens to point sources of light in front of a convex lens?

    <p>They create a distinct point focus on the opposite side.</p> Signup and view all the answers

    What is the result of focusing light from multiple point sources through a convex lens?

    <p>A range of color variations is displayed.</p> Signup and view all the answers

    What determines the distinct point focus created by each point source in front of a convex lens?

    <p>The alignment of the sources with the lens center.</p> Signup and view all the answers

    What determines the refractive index of a substance?

    <p>The velocity of light in the solid compared to air</p> Signup and view all the answers

    What occurs to light rays that strike the center of a convex lens?

    <p>They pass through without being refracted</p> Signup and view all the answers

    What phenomenon occurs at the edges of a convex lens when light rays are entering?

    <p>The rays bend increasingly toward the center</p> Signup and view all the answers

    When light travels through a transparent substance with a refractive index of 1.50, how does its speed compare to the speed of light in air?

    <p>It travels slower than in air</p> Signup and view all the answers

    What is the effect of the angle at which light rays strike a lens's surface?

    <p>It influences the degree of refraction of the rays</p> Signup and view all the answers

    What occurs to the lens shape when the ciliary muscle relaxes?

    <p>The lens assumes a more spherical shape.</p> Signup and view all the answers

    What is presbyopia?

    <p>A condition where the lens can no longer accommodate for near and far vision.</p> Signup and view all the answers

    How does the amount of light entering the eye through the pupil relate to its diameter?

    <p>It increases with the square of the diameter of the pupil.</p> Signup and view all the answers

    What role does parasympathetic nerve stimulation play in vision?

    <p>It contracts the ciliary muscle, allowing the lens to thicken.</p> Signup and view all the answers

    At what diameter can the human pupil vary?

    <p>From 1.5 mm to 8 mm.</p> Signup and view all the answers

    Why might older individuals require bifocal glasses?

    <p>To accommodate for both near and far vision due to presbyopia.</p> Signup and view all the answers

    What happens as a distant object moves closer to the eye?

    <p>Parasympathetic impulses to the ciliary muscle must increase.</p> Signup and view all the answers

    Which of the following describes the primary function of the iris?

    <p>To control the amount of light entering the eye.</p> Signup and view all the answers

    What is a primary characteristic of the ciliary muscle's control?

    <p>It is controlled by parasympathetic nerves.</p> Signup and view all the answers

    What determines the fixed focus distance experienced by a presbyopic person?

    <p>The physical characteristics of each person's eyes.</p> Signup and view all the answers

    The refractive index of a transparent substance is determined by the ratio of the velocity of light in the substance to the velocity of light in air.

    <p>False</p> Signup and view all the answers

    A convex lens causes light rays to diverge towards the edges.

    <p>False</p> Signup and view all the answers

    Light rays travel slower in transparent solids and liquids than in air.

    <p>True</p> Signup and view all the answers

    The outer light rays striking a convex lens bend toward the center due to a phenomenon called divergence.

    <p>False</p> Signup and view all the answers

    The refractive index of air is 1.00, meaning light travels at its maximum speed in air.

    <p>True</p> Signup and view all the answers

    When light rays enter a medium at a perpendicular interface, they change their velocity but do not bend.

    <p>True</p> Signup and view all the answers

    In a medium with a refractive index of 1.50, light travels at a speed of 300,000 km/sec.

    <p>False</p> Signup and view all the answers

    The degree of refraction increases with the difference in refractive indices of two media.

    <p>True</p> Signup and view all the answers

    Refraction occurs at interfaces only when light rays travel from a slower medium to a faster medium.

    <p>False</p> Signup and view all the answers

    The wave front of light rays bending at an angulated interface will always remain vertical.

    <p>False</p> Signup and view all the answers

    A camera lens focuses images on film by reversing the image upside down.

    <p>True</p> Signup and view all the answers

    A lens with a strength of +2 diopters bends parallel light rays twice as much as a lens with a strength of +1 diopter.

    <p>True</p> Signup and view all the answers

    The refractive power of a lens is generally measured in terms of feet.

    <p>False</p> Signup and view all the answers

    A convex lens creates a focal point 0.5 meters beyond the lens if it has a refractive power of +2 diopters.

    <p>True</p> Signup and view all the answers

    A lens that diverges light rays has a positive refractive power.

    <p>False</p> Signup and view all the answers

    Using two convex cylindrical lenses at right angles creates a common point focus.

    <p>True</p> Signup and view all the answers

    The refractive power of a lens is determined by its physical length.

    <p>False</p> Signup and view all the answers

    Light rays that pass through the center of a convex lens are affected by the curvature of the lens.

    <p>False</p> Signup and view all the answers

    An image formed by a convex lens placed at its focus distance is upright.

    <p>False</p> Signup and view all the answers

    A lens that converges parallel rays to a focal point 10 centimeters beyond it has a refractive power of +10 diopters.

    <p>False</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Refraction = Bending of light rays at an angulated interface Wave fronts = Surfaces connecting points of equal phase in a wave Refractive index = A measure of how much light slows down in a medium Focal length = The distance from a lens at which parallel rays converge</p> Signup and view all the answers

    Match the following materials with their respective refractive indices:

    <p>Air = 1.00 Glass = 1.50 Water = 1.33 Diamond = 2.42</p> Signup and view all the answers

    Match the descriptions with the corresponding light ray behavior:

    <p>Light rays entering perpendicular to the surface = No deviation from their course Light rays entering at an angle = Rays bend due to different refractive indices Wave front traveling in air = Moves at 300,000 km/sec Wave front traveling in glass = Moves at 200,000 km/sec</p> Signup and view all the answers

    Match the following concepts with their relevant figures:

    <p>Figure 50-1A = Light rays entering a glass surface perpendicular Figure 50-1B = Light rays striking an angulated glass surface Figure 50-2 = Bending of light rays at a convex lens Wave fronts in glass = Shorter distances between wave fronts</p> Signup and view all the answers

    Match the following actions with their outcomes in light behavior:

    <p>Passing through an angulated interface = Light rays bend Entering two different media = Change in velocity and wavelength Striking the center of a lens = Minimal deviation Focusing parallel rays = Convergence at a focal point</p> Signup and view all the answers

    Match the following characteristics of a convex lens with their descriptions:

    <p>Convergence of light rays = Brings light rays to a point focus Passing through the center = Light rays are not refracted Image formation = Mosaic of point sources in an object Effect of convexity = Changes how light is focused</p> Signup and view all the answers

    Match the following scenarios with their outcomes when using a convex lens:

    <p>Parallel rays entering the lens = Focused at the same distance Diverging rays entering the lens = Also focused at a point Point source of light = Creates distinct point focus Object in front of lens = Appears as a mosaic of light</p> Signup and view all the answers

    Match the following terms related to convex lenses with their meanings:

    <p>Focal point = Distance where light rays converge Optical center = Point where light passes without refraction Convexity = Curvature affecting how light is focused Light mosaic = Collection of bright and weak light points</p> Signup and view all the answers

    Match the types of light rays with their behaviors through a convex lens:

    <p>Diverging rays = Focused by the lens to a point Parallel rays = Converged to a common focal point Point sources = Each creates its own point focus Light rays at edges = May behave differently than center rays</p> Signup and view all the answers

    Match the following aspects of light behavior through a convex lens:

    <p>Image from point source = Appears directly in line with the source and lens center Center passage of rays = No refraction occurs Collection of light points = Forms the image seen Lens type overall = Can change how incoming rays are focused</p> Signup and view all the answers

    Study Notes

    Lens and Light

    • Convex Lens: Converges parallel light rays at a focal point.
    • Concave Lens: Diverges parallel light rays.
    • Cylindrical Lens: Bends light rays in only one plane, creating a line focus.
    • Two Cylindrical Lenses: Crossed at right angles, have the same function as a spherical lens.

    Focal Length

    • Focal length: Distance at which parallel rays converge to a focal point.
    • Diverging Rays: Focal distance is farther from the lens than the focal length for parallel rays.

    Refractive Power

    • Refractive Power: Measured in diopters.
    • +10 diopters: Lens focuses parallel light rays 10 cm beyond the lens.
    • Concave Lenses: Diverge light, have negative dioptric strengths.
    • Concave and Convex Lens Combination: Can neutralize each other's refractive power.

    The Eye as a Camera

    • Eye's Refractive Power: Approx. 59 diopters.
    • Eye's Components: Cornea, aqueous humor, lens, vitreous humor.
    • Each component has different refractive power: Cornea (1 diopter), lens (10 diopters), aqueous humor (2 diopters), vitreous humor (1 diopter) and Air (1 diopter).

    Refraction of Light

    • The refractive index of a substance is the ratio of the speed of light in air to the speed of light in that substance.
    • Light bends when it passes from one medium to another with a different refractive index. This bending is called refraction.
    • The amount of bending depends on the difference in refractive indices and the angle of incidence.
    • A convex lens converges light rays, focusing parallel light rays at a point called the focal point.

    Accommodation for Near Vision

    • The lens of the eye can change shape to focus on objects at different distances, a process called accommodation.
    • The ciliary muscle contracts, relaxing the ligaments attached to the lens capsule. This allows the lens to become more spherical, increasing its refractive power.
    • Accommodation is controlled by parasympathetic nerves.
    • As a person ages, the lens loses elasticity, making it harder to accommodate for near vision. This condition is called presbyopia.

    Pupillary Diameter

    • The iris controls the amount of light entering the eye by changing the size of the pupil.
    • The pupil can range in diameter from 1.5mm to 8mm.
    • A smaller pupil increases the depth of focus, meaning the retina can be displaced from the focal plane without causing blurring.

    Errors of Refraction

    • Emmetropia is normal vision where parallel light rays focus on the retina when the ciliary muscle is relaxed.
    • Hyperopia (farsightedness) occurs when parallel light rays focus behind the retina. This is corrected by convex lenses.
    • Myopia (nearsightedness) occurs when parallel light rays focus in front of the retina. This is corrected by concave lenses.
    • Astigmatism occurs when the cornea has an uneven curvature, causing light to focus at different points on the retina. This is corrected by cylindrical lenses.

    Cataracts

    • Cataracts occur when the lens of the eye becomes cloudy, impairing vision.
    • This clouding can be caused by aging, injury, or disease.
    • Cataracts can be removed surgically, which involves replacing the lens with an artificial lens.

    Refraction of Light

    • The refractive index of a transparent substance is the ratio of the speed of light in air to the speed of light in the substance.
    • Light rays bend when entering a medium with a different refractive index.
    • The degree of bending (refraction) increases with a greater difference in refractive indices between the two media and with a greater angulation between the interface and the entering wave front.

    Convex Lens Focuses Light Rays

    • Convex lenses converge parallel light rays to a point called a focal point (focus).
    • The focal length is the distance between the lens and the focal point.
    • The refractive power of a lens is measured in diopters, where 1 diopter = 1 meter / focal length.

    Depth of Focus

    • The depth of focus is the range of distances in front of the lens over which objects appear to be clearly focused.
    • Objects closer than the near point are not in focus.
    • Objects farther than the far point are not in focus.

    Accommodation

    • Accommodation is the process of adjusting the shape of the lens to focus objects at different distances.
    • This is achieved by the ciliary muscles contracting/relaxing, changing the tension on the suspensory ligaments that hold the lens.
    • Near vision requires a thicker, rounder lens.
    • Far vision requires a thinner, flatter lens.

    Myopia (Nearsightedness)

    • Occurs when the eye is too long or the lens has too much refractive power.
    • Light rays are focused in front of the retina, causing blurry vision for distant objects.
    • Corrected with concave lenses.

    Hyperopia (Farsightedness)

    • Occurs when the eye is too short or the lens has too little refractive power.
    • Light rays are focused behind the retina, causing blurry vision for near objects.
    • Corrected with convex lenses.

    Astigmatism

    • Occurs when the cornea has a different curvature in one plane compared to the other.
    • Vision is blurred at all distances.
    • Corrected with cylindrical lenses.

    Cataracts

    • Occurs from clouding of the eye's lens, interfering with light passage.
    • Can be corrected by surgically removing the clouded lens and inserting a clear artificial lens.

    Light Travel and Refraction

    • Light rays travel in a beam and strike an interface. If the interface is perpendicular to the beam, they travel through with decreased velocity and shorter wavelength.
    • If the interface is angulated, the rays bend, the degree of refraction increases with the difference in refractive index of the two mediums.
    • Light travels perpendicular to the plane of the wave front, bending downward.

    Convex Lenses

    • Bending of light rays at the surface of a convex lens focuses parallel light rays to a focal point.
    • Convex lens can focus both parallel and diverging rays at the same distance.
    • A point source of light is focused, by a convex lens, on the opposite side of the lens, directly in line with the point source.
    • Objects in front of the lens are a mosaic of point sources of light, each focused at a separate point on the opposite side of the lens in line with the lens center.

    Eye Focusing

    • Lens accommodation is the ability of the eye to focus on objects at varying distances
    • The lens is held in place by ligaments attached to the ciliary muscle
    • Contraction of the ciliary muscle relaxes the ligaments, allowing the lens to become more spherical and increase refractive power.

    Presbyopia

    • With age, the lens loses elasticity and becomes less accommodating.
    • Presbyopia: lens changes shape, becoming less spherical.

    Pupillary Diameter

    • Iris controls the amount of light entering the eye by adjusting the pupil size.
    • Pupil diameter can vary from 1.5 to 8 millimeters.

    Astigmatism

    • Astigmatism is caused by uneven curvature of the cornea or lens, causing light rays to not focus at a single point.
    • Light rays focus at different distances in different planes.
    • A cylindrical lens is used to correct astigmatism.

    Cataracts

    • Cataracts are clouding of the lens.
    • Cataracts obstruct light transmission, leading to blurry vision.
    • Surgical removal of the lens corrects cataracts.

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    Guyton and Hall Physiology Chapter 50 - The Eye I. PDF

    Description

    Explore the principles of lenses and their properties in this quiz. Learn about convex, concave, and cylindrical lenses, as well as the concepts of focal length and refractive power. Test your knowledge on how the human eye functions as a camera and the role of different components.

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