Question

The uncorrected eye. For the following questions, assume that the distance between the eye lens and the retina is 1.70 cm. In other words, since the image is always formed on the retina, the distance between the lens and the image is always 1.70 cm. Also note that, as is seen in the ray diagram, since the eye lens is converging and the image is on the opposite side of the lens compared to the object, the image is always real.

a. What is the focal length of the eye when an object is 25.0 cm away from the eye lens? \

b. What is the focal length of the eye when an object is very far away from the eye lens (object at infinity)?

c. One nearsighted patient has a far point of 400 cm. What is the focal length of her eye when an object is at her far point? How does this focal length compare to the focal length in part b?

d. One farsighted patient has a near point of 40.0 cm. What is the focal length of his eye when an object is at his near point? How does this focal length compare to the focal length in part a?

e. The nearsighted patient in part c tries to view an object that is very far away (object at infinity). Use the focal length calculated in part c to determine the location of the image. How does this compare to the distance from the eye lens to the retina? What kind of image is seen on the retina?

f. The farsighted patient in part d tries to view an object 25 cm away from his eye, which a person with normal vision can see clearly. Use the focal length calculated in part d to determine the location of the image. How does this compare to the distance from the eye lens to the retina? What kind of image is seen on the retina?

Answer #1

1) The distance from the lens to the retina is 3.1 cm, what is
the effective focal length of the lens when staring at an object
infinitely far away?
2) An object is moved to 40cm from the eye. What must the focal
length of the eye be to focus the image on the retina?
3) In the near sighted eye, images focus before hitting the
retina. Suppose the focal length of the lens is 1.9 cm, while the
distance...

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 50.0 cm from his eyes
instead of the usual 25.0 cm .
Part A
Is this person nearsighted or farsighted?
Is this person nearsighted or farsighted?
This person is nearsighted.
This person is farsighted....

A. The human eye 1. Whenever a normal eye forms an image, the
image distance will always equal the distance from the cornea and
eye lens to the retina (~25 mm), regardless of how far away the
object is located. Explain why the image distance cannot change. 2.
If the image distance must change, then what intrinsic property of
the eye lens must change in order for the eye to focus on objects
at different distances? Hint: read the Introduction....

A person is farsighted and has near point of 50 cm. Retina is at
a distance L = 1.7 cm. When wearing contact lenses and reading a
book 30 cm in front of the eye, what is the object distance for the
lenses? What is the desired image distance? Is the magnitude of the
image distance a minimum, maximum, or the only acceptable image
distance? Find the focal length and refractive power of the contact
lens that will fix this...

1. What is the optical power of the eye when viewing an object
from a distance of 23.5 cm?
2.What is the far point for a person whose eyes have a relaxed
power of 50.25 D?
3. What power lens is required to correct a myopic (nearsighted)
eye with a far point of 6.50 m? Neglect the distance between the
corrective lens and the eye.
4. What power lens is required to correct a hyperopic
(farsighted) eye with a...

1. Consider a 1 mm bug located at your nearpoint, 25 cm away
from your left eye. 1a). Sketch the object, lens and image
positions if the object is 1 mm in size and the image distance
between the retina and lens in your eye is 1 cm. 1b). What focal
length for your eye lens is needed to focus the bugâ€™s image onto
your retina? 1c). If you insert a convex magnifying glass 6 cm away
from the bug,...

Q2. Lenses and the Eye
An object O is positioned 3.5 m from a lens of focal
length f = -1.5 m as shown:
Copy the diagram and draw in:
the path of a parallel ray from the top of the object through
the lens;
the path of a ray through the centre of the lens;
and hence the location of the image.
Calculate the image distance di from the
lens. Mark this distance on the diagram in a).
A...

A farsighted eye is corrected by placing a converging lens in
front of the eye. The lens will create a virtual image that is
located at the near point (the closest an object can be and still
be in focus) of the viewer when the object is held at a comfortable
distance, usually taken to be 25.0 cm.25.0 cm. If a person has a
near point of 49.5 cm,49.5 cm, what power reading glasses should be
prescribed to treat this...

The distance from the eye lens (i.e. cornea-lens system) to the
retina of a particular eye is 2.02 cm. The power of the eye lens
when it is relaxed is 54.1 D.
(a) Calculate the far point of the eye. (m)
(b) If a corrective lens is to be placed 1.78 cm from the eye,
calculate the power of the corrective lens that will allow the eye
to focus on distant objects. (D)

The far point of an eye is 185 cm. A corrective lens is to be
used to allow this eye to focus clearly on objects a great distance
away. What should be the focal length of this lens?
What is the power of the needed corrective lens in diopters?

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