Textbook Question
A camera lens has a focal length of 180.0 mm and an aperture diameter of 16.36 mm. What is the ƒ-number of the lens?
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Ch 34: Geometric Optics
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610
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Table of contents
- Ch 01: Units, Physical Quantities & Vectors41
- Ch 02: Motion Along a Straight Line67
- Ch 03: Motion in Two or Three Dimensions47
- Ch 04: Newton's Laws of Motion23
- Ch 05: Applying Newton's Laws59
- Ch 06: Work & Kinetic Energy14
- Ch 07: Potential Energy & Conservation8
- Ch 08: Momentum, Impulse, and Collisions18
- Ch 09: Rotation of Rigid Bodies42
- Ch 10: Dynamics of Rotational Motion48
- Ch 11: Equilibrium & Elasticity27
- Ch 12: Fluid Mechanics31
- Ch 13: Gravitation35
- Ch 14: Periodic Motion32
- Ch 15: Mechanical Waves25
- Ch 16: Sound & Hearing32
- Ch 17: Temperature and Heat36
- Ch 18: Thermal Properties of Matter38
- Ch 19: The First Law of Thermodynamics33
- Ch 20: The Second Law of Thermodynamics22
- Ch 21: Electric Charge and Electric Field36
- Ch 22: Gauss' Law24
- Ch 23: Electric Potential31
- Ch 24: Capacitance and Dielectrics18
- Ch 25: Current, Resistance, and EMF26
- Ch 26: Direct-Current Circuits30
- Ch 27: Magnetic Field and Magnetic Forces18
- Ch 28: Sources of Magnetic Field10
- Ch 29: Electromagnetic Induction28
- Ch 30: Inductance17
- Ch 31: Alternating Current21
- Ch 32: Electromagnetic Waves1
- Ch 33: The Nature and Propagation of Light20
- Ch 34: Geometric Optics34
- Ch 35: Interference19
- Ch 36: Diffraction25
- Ch 37: Special Relativity20
- Ch 38: Photons: Light Waves Behaving as Particles15
- Ch 39: Particles Behaving as Waves26
- Ch 40: Quantum Mechanics I: Wave Functions21
- Ch 41: Quantum Mechanics II: Atomic Structure25
- Ch 42: Molecules and Condensed Matter18
- Ch 43: Nuclear Physics16
- Ch 44: Particle Physics and Cosmology23
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610Not the one you use?Change textbook
Chapter 34, Problem 52a
Contact lenses are placed right on the eyeball, so the distance from the eye to an object (or image) is the same as the distance from the lens to that object (or image). A certain person can see distant objects well, but his near point is 45.0 cm from his eyes instead of the usual 25.0 cm. Is this person nearsighted or farsighted?
Verified step by step guidance1
Step 1: Begin by understanding the terms 'nearsighted' and 'farsighted.' Nearsightedness (myopia) means a person can see nearby objects clearly but struggles to see distant objects. Farsightedness (hyperopia) means a person can see distant objects clearly but struggles to see nearby objects.
Step 2: Analyze the problem. The person can see distant objects well, but their near point is farther than the usual 25.0 cm. This indicates difficulty in seeing nearby objects, which is a characteristic of farsightedness.
Step 3: Relate the near point to the condition. A normal near point is 25.0 cm, but this person’s near point is 45.0 cm. This extended near point confirms that the person is farsighted.
Step 4: Conclude that the person is farsighted based on the given information and the definition of farsightedness.
Step 5: If needed, discuss corrective measures. Farsightedness is typically corrected using converging lenses (convex lenses) to reduce the near point distance and allow the person to focus on nearby objects.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nearsightedness and Farsightedness
Nearsightedness (myopia) occurs when the eye is too long or the cornea is too curved, causing distant objects to appear blurry while near objects are seen clearly. Farsightedness (hyperopia) is the opposite, where the eye is too short or the cornea is too flat, making it difficult to see close objects clearly while distant objects may be seen well. Understanding these conditions is crucial for determining the type of vision correction needed.
Near Point
The near point is the closest distance at which the eye can focus on an object clearly. For a typical young adult, this distance is about 25 cm. If a person's near point is farther away, such as 45 cm, it indicates a problem with focusing on nearby objects, which is a characteristic of farsightedness.
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Optical Correction
Optical correction involves using lenses to adjust the focal point of light entering the eye, allowing for clearer vision. For nearsighted individuals, concave lenses are used to diverge light rays, while convex lenses are used for farsighted individuals to converge light rays. Identifying the type of vision impairment helps in selecting the appropriate corrective lenses.
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Related Practice
Textbook Question
BIO A person can see clearly up close but cannot focus on objects beyond 75.0 cm. She opts for contact lenses to correct her vision. Is she nearsighted or farsighted?
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Textbook Question
Where is the near point of an eye for which a contact lens with a power of +2.75 diopters is prescribed?
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Textbook Question
Zoom Lens. Consider the simple model of the zoom lens shown in Fig. 34.43a. The converging lens has focal length f1 = 12 cm, and the diverging lens has focal length f2 = -12 cm. The lenses are separated by 4 cm as shown in Fig. 34.43a. (a) For a distant object, where is the of the converging lens? (c) Where is the final image? Compare your answer to Fig. 34.43a.
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Textbook Question
BIO A person can see clearly up close but cannot focus on objects beyond 75.0 cm. She opts for contact lenses to correct her vision. What focal length contact lens is needed, and what is its power in diopters?
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Textbook Question
BIO Ordinary Glasses. Ordinary glasses are worn in front of the eye and usually 2.0 cm in front of the eyeball. Suppose that the person in Exercise 34.52 prefers ordinary glasses to contact lenses. What focal length lenses are needed to correct his vision, and what is their power in diopters?
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