Problem 23
Suppose that the lens system (cornea + lens) in a particular eye has a focal
length that can vary between \(1.85 \mathrm{cm}\) and \(2.00 \mathrm{cm},\) but
the distance from the lens system to the retina is only \(1.90 \mathrm{cm} .\)
(a) Is this eye nearsighted or farsighted? Explain. (b) What range of
distances can the eye see clearly without corrective lenses?
Problem 25
The uncorrected far point of Colin's eye is \(2.0 \mathrm{m} .\) What refractive power contact lens enables him to clearly distinguish objects at large distances?
Problem 26
The distance from the lens system (cornea + lens) of a particular eye to the
retina is \(1.75 \mathrm{cm} .\) What is the focal length of the lens system
when the eye produces a clear image of an object \(25.0 \mathrm{cm}\) away?
Problem 27
A nearsighted man cannot clearly see objects more than \(2.0 \mathrm{m}\) away.
The distance from the lens of the eye to the retina is \(2.0 \mathrm{cm},\) and
the eye's power of accommodation is \(4.0 \mathrm{D}\) (the focal length of the
cornea-lens system increases by a maximum of \(4.0 \mathrm{D}\) over its relaxed
focal length when accommodating for nearby objects). (a) As an amateur
optometrist, what corrective eyeglass lenses would you prescribe to enable him
to clearly see distant objects? Assume the corrective lenses are $2.0
\mathrm{cm}$ from the eyes. (b) Find the nearest object he can see clearly
with and without his glasses.
Problem 28
A nearsighted man cannot clearly see objects more than \(2.0 \mathrm{m}\) away.
The distance from the lens of the eye to the retina is \(2.0 \mathrm{cm},\) and
the eye's power of accommodation is \(4.0 \mathrm{D}\) (the focal length of the
cornea-lens system increases by a maximum of \(4.0 \mathrm{D}\) over its relaxed
focal length when accommodating for nearby objects). (a) As an amateur
optometrist, what corrective eyeglass lenses would you prescribe to enable him
to clearly see distant objects? Assume the corrective lenses are $2.0
\mathrm{cm}$ from the eyes. (b) Find the nearest object he can see clearly
with and without his glasses.
Problem 29
Angular Magnification and the Simple Magnifier
Thomas wants to use his 5.5 -D reading glasses as a simple magnifier. What is
the angular magnification of this lens when Thomas's eye is relaxed?
Problem 30
(a) What is the focal length of a magnifying glass that gives an angular
magnification of 8.0 when the image is at infinity? (b) How far must the
object be from the lens? Assume the lens is held close to the eye.
Problem 31
Keesha is looking at a beetle with a magnifying glass. She wants to see an
upright, enlarged image at a distance of \(25 \mathrm{cm} .\) The focal length
of the magnifying glass is \(+5.0 \mathrm{cm} .\) Assume that Keesha's eye is
close to the magnifying glass. (a) What should be the distance between the
magnifying glass and the beetle? (b) What is the angular magnification?
(tutorial: magnifying glass II).
Problem 32
Callum is examining a square stamp of side \(3.00 \mathrm{cm}\) with a
magnifying glass of refractive power \(+40.0 \mathrm{D}\). The magnifier forms
an image of the stamp at a distance of \(25.0 \mathrm{cm} .\) Assume that
Callum's eye is close to the magnifying glass. (a) What is the distance
between the stamp and the magnifier? (b) What is the angular magnification?
(c) How large is the image formed by the magnifier?
Problem 34
An insect that is 5.00 mm long is placed \(10.0 \mathrm{cm}\) from a converging
lens with a focal length of \(12.0 \mathrm{cm} .\) (a) What is the position of
the image? (b) What is the size of the image? (c) Is the image upright or
inverted? (d) Is the image real or virtual? (e) What is the angular
magnification if the lens is close to the eye?
