Optics

Question Answers

A man is unable to focus on objects nearer than 1.5 m. (a) Does he have (1) nearsightedness, (2) farsightedness, or (3) astigmatism? Explain. (b) The type of contact lenses that allows him to focus on the print of a book held 25 cm from his eyes should be (1) converging, (2) divergi...
A woman cannot see objects clearly when they are farther than 12.5 m away. (a) Does she have (1) near-sightedness, (2) farsightedness, or (3) astigmatism? Explain. (b) Which type of lens will allow her to see distant objects clearly, and of what power should the lens be? ...
To correct a case of farsightedness, an optometrist prescribes converging contact lenses that effectively move the patient’s near point from 85 cm to 25 cm. (a) What is the power of the lenses? (b) To see distant objects clearly, should the patient wear the contact lenses or take ...
The amount of light that reaches the film in a camera depends on the lens aperture (the effective area) as con-trolled by the diaphragm. The f-number is the ratio of the focal length of the lens to its effective diameter. For example, an f/8 setting means that the diameter of the aper...
A refracting telescope has an objective with a focal length of 50 cm and an eyepiece with a focal length of 2.0 cm. The telescope is used to view an object that is 10 cm high and located 50 m away. What is the apparent angular height, in degrees, of the object as viewed through the te...
Two astronomical telescopes have the characteristics shown in the following table: ...
A person with nearsightedness was prescribed with con-tact lenses of power – 2.0 D. By mistake, he was given lenses of power + 2.0 D. What is the range of object distances that this person can see clearly with the wrong lenses? ...
Referring to Fig. 25.25, show that the angular magnification of a refracting telescope focused for the final image at infinity is m = – fo/fe. (Because telescopes are designed for viewing distant objects, the angular size of an object viewed with the unaided eye is the angular size ...
Referring to Fig. 25.24, show that the magnifying power of a magnifying glass held at a distance d from the eye is given by when the actual object is located at the near point (25 cm). ...
A person can just see the print in a book clearly when she holds the book no closer than at arm’s length (0.45 m from the eyes). (a) Does she have (1) nearsightedness, (2) farsightedness, or (3) astigmatism? Explain. (b) Which type of lens will allow her to read the text at the no...

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