Question 1

Two thin lenses have powers P₁ and P₂, measured in diopters. If these lenses are placed in contact with one another, the resulting power is: A)more than both P₁ and P₂. B)less than both P₁ and P₂. C)half-way between P₁ and P₂. D)P₁ + P₂.

Accepted Answer

When two lenses are placed in contact with each other, their powers add up. Therefore, the resulting power is equal to the sum of the powers of the two lenses. Thus, the resulting power is P₁ + P₂. Therefore, the best choice is D.

Question 2

While a camera has film where the image is formed, the eye forms the image on the:
A)pupil.
B)cornea.
C)retina.
D)optic nerve.

Accepted Answer

The image formed by the eye is projected onto the retina, where it is received and processed by specialized cells to be sent to the brain through the optic nerve. The pupil is simply the opening that allows light to enter the eye, while the cornea helps to focus light onto the retina.

Question 3

Which term identifies the defect where the lens produces a line image of a point source?
A)myopia
B)presbyopia
C)hyperopia
D)astigmatism

Accepted Answer

Astigmatism is the defect where the lens produces a line image of a point source, rather than a point image. Myopia, hyperopia, and presbyopia all involve issues with the overall focus of the lens, rather than the shape of the image produced.

Question 4

A given individual is unable to see objects clearly when they are beyond 100 cm.What focal length lens should be used to correct this problem?
A)-100 cm
B)-33.3 cm
C)-20 cm
D)75 cm

Accepted Answer

The answer of A given individual is unable to see...

Question 5

You are designing eyeglasses for someone whose near point is 70 cm.What focal length lens should you prescribe so that an object can be clearly seen when placed at 25 cm in front of the eye?
A)-18 cm
B)18 cm
C)39 cm
D)70 cm

Accepted Answer

Using the formula 1/f = 1/do + 1/di, where do is the object distance (25 cm), di is the image distance (70 cm), and f is the focal length of the lens, we can solve for f:

1/f = 1/25 + 1/70

1/f = 0.06

f = 16.7 cm

Therefore, the closest choice is C, which is 39 cm.

Question 6

A farsighted person with astigmatism would be prescribed a lens that is:
A)diverging only.
B)both converging and cylindrical.

Accepted Answer

A person with astigmatism has an irregularly shaped cornea, which means incoming light does not focus properly on the retina. Correcting this requires a cylindrical lens that can refract light differently in different directions. A farsighted person requires a converging lens to focus light on the retina. Therefore, a person with both conditions would require a lens that is both converging and cylindrical.

Question 7

Young children that need glasses are rarely prescribed bifocals.Why?
A)They are almost always nearsighted.
B)They are almost always farsighted.
C)They have considerable accommodation power.
D)Parents don't go for the additional expense.

Accepted Answer

Young children have a strong ability to accommodate, meaning they can easily adjust the focus of their eyes to see objects up close or far away. Therefore, bifocals are typically not necessary as they can adjust for near and far vision without the need for a separate lens.

Question 8

Two thin lenses in combination are placed in contact with each other along a common axis.They have powers of 50 and -30 diopters, respectively.What is their combined power?
A)10 diopters
B)20 diopters
C)80 diopters
D)-10 diopters

Accepted Answer

The answer of Two thin lenses in combination are placed...

Question 9

If a person is farsighted the corrective lens will:
A)take an object at the near point and form an image at 25 cm.
B)take an object at 25 cm and form an image at the near point.
C)take an object at infinity and form an image at 25 cm.
D)take an object at infinity and form an image at the near point.

Accepted Answer

The answer of If a person is farsighted the corrective...

Question 10

A nearsighted person cannot see objects clearly beyond 70 cm (the far point).If the patient has no astigmatism and contact lenses are prescribed, what is the power of the lens required to correct the patient's vision?
A)-0.7 diopters
B)-1.4 diopters
C)-2.9 diopters
D)-7.0 diopters

Accepted Answer

The answer of A nearsighted person cannot see objects clearly...

Question 11

If a person has hyperopia that person:
A)may have an unusually long eyeball.
B)cannot see near objects clearly.
C)cannot relax the ciliary muscle adequately.
D)cannot form images behind the retina.

Accepted Answer

Hyperopia, also known as farsightedness, is a refractive error where a person has difficulty seeing objects up close. This occurs because the eyeball is too short, causing the image to focus behind the retina instead of directly on it. This can make it difficult for the person to focus on near objects, while distant objects may appear clearer.

Question 12

A thin lens of focal length 20 cm is placed in contact with a 20-diopter thin lens. What is the power of the combined lenses?
A)1/2 diopter
B)15 diopters
C)25 diopters
D)40 diopters

Accepted Answer

To find the power of combined lenses, we use the formula:
P_total = P1 + P2 - (d/P1*P2)
where P1 and P2 are the power of individual lenses and d is the distance between the two lenses.
Here, P1 = 20 diopters and P2 = 1/20 meter^-1 = 20 diopters (as f=20 cm).
Also, the lenses are in contact, so d = 0.
Putting these values in the formula, we get:
P_total = 20 + 20 - (0/20*20) = 40 diopters
Therefore, the power of the combined lenses is 40 diopters.

Question 13

A lens with a focal length of 10 cm has what power?
A)10.0 diopters
B)0.1 diopters
C)1 diopters
D)-10.0 diopters

Accepted Answer

The answer of A lens with a focal length of...

Question 14

Which eye defect is corrected by a lens having different curvatures in two perpendicular directions?
A)myopia
B)presbyopia
C)hyperopia
D)astigmatism

Accepted Answer

Astigmatism is a refractive error in which the curvature of the cornea is uneven, causing blurry or distorted vision. A lens with different curvatures in two perpendicular directions can correct this irregularity in the cornea and improve the clarity of vision.

Question 15

A person with limited accommodation is prescribed lenses of power -1.0 diopters for distant vision. Bifocal inserts are added to these lenses to allow vision at 30 cm. What is the power of the inserts?
A)2.3 diopters
B)3.3 diopters
C)4.3 diopters
D)This does not work with negative diopter distance lenses.

Accepted Answer

The power of the bifocal inserts can be calculated using the formula: power of inserts = (1 / desired focal length) - (1 / distance power). The desired focal length is 30 cm, which is equivalent to 3.33 diopters. The distance power is -1.0 diopters. Therefore, the power of the inserts is (1/3.33) - (1/-1.0) = 0.3 + 1.0 = 1.3 diopters. Adding this to the distance power of -1.0 gives a total power of 0.3 diopters for the bifocal inserts, which is equivalent to 3.3 diopters. Therefore, the correct answer is B.

Question 16

In the normal eye the ciliary muscles that control the lens will relax:
A)when viewing objects at the near point.
B)when viewing objects at infinity.
C)when viewing objects at a distance of 20 ft.
D)only when a person has his/her eyes closed.

Accepted Answer

The ciliary muscles relax when viewing objects at infinity, as the lens needs to be flattened in order to focus on distant objects. When viewing objects at the near point, the ciliary muscles contract in order to round the lens and focus on the close object. When viewing objects at a distance of 20 ft, the ciliary muscles are in a state of rest, but not necessarily fully relaxed. And the ciliary muscles can relax when a person has their eyes closed, but this is not the only circumstance where they will relax.

Question 17

Glaucoma occurs because:
A)the eye cannot accommodate properly.
B)the shape or size of the eye is not normal.
C)there is too much pressure in the fluid in the eyeball.
D)the lens is partially or totally opaque.

Accepted Answer

Glaucoma occurs when there is an increase in fluid pressure in the eyeball. This can occur due to blockages in the drainage pathways or overproduction of the fluid. It is not related to the accommodation of the eye, the shape or size of the eye, or the opacity of the lens.

Question 18

The eye changes its f-number by:
A)using the iris to change the size of the pupil.
B)using the ciliary muscle to change the focal length of the lens.
C)Both a & b are correct.
D)The eye does not change its f-number.

Accepted Answer

The eye changes its f-number by both using the iris to change the size of the pupil and using the ciliary muscle to change the focal length of the lens. The size of the pupil determines the amount of light that enters the eye, while changing the focal length of the lens alters the position of the focal point of light entering into the eye. These two mechanisms work together to adjust the amount of light reaching the retina and to create a clear image.

Question 19

A person has a near point of 40 cm and a far point of 2.0 m. When looking through lenses of focal length -2.0 m, what is the nearest an object can be to be seen clearly?
A)33 cm
B)50 cm
C)100 cm
D)240 cm

Accepted Answer

The answer of A person has a near point of...

Question 20

The "normal" eye has a near point of 25 cm.If a given individual's near point is 73 cm, for what problem will the eye doctor prescribe correction?
A)myopia
B)presbyopia
C)hyperopia
D)astigmatism

Accepted Answer

The answer of The "normal" eye has a near point...

Quiz 25: Optical Instruments

Two thin lenses have powers P₁ and P₂, measured in diopters. If these lenses are placed in contact with one another, the resulting power is:

While a camera has film where the image is formed, the eye forms the image on the:

Which term identifies the defect where the lens produces a line image of a point source?

A given individual is unable to see objects clearly when they are beyond 100 cm.What focal length lens should be used to correct this problem?

You are designing eyeglasses for someone whose near point is 70 cm.What focal length lens should you prescribe so that an object can be clearly seen when placed at 25 cm in front of the eye?

A farsighted person with astigmatism would be prescribed a lens that is:

Young children that need glasses are rarely prescribed bifocals.Why?

Two thin lenses in combination are placed in contact with each other along a common axis.They have powers of 50 and -30 diopters, respectively.What is their combined power?

If a person is farsighted the corrective lens will:

A nearsighted person cannot see objects clearly beyond 70 cm (the far point) .If the patient has no astigmatism and contact lenses are prescribed, what is the power of the lens required to correct the patient's vision?

If a person has hyperopia that person:

A thin lens of focal length 20 cm is placed in contact with a 20-diopter thin lens. What is the power of the combined lenses?

A lens with a focal length of 10 cm has what power?

Which eye defect is corrected by a lens having different curvatures in two perpendicular directions?

A person with limited accommodation is prescribed lenses of power -1.0 diopters for distant vision. Bifocal inserts are added to these lenses to allow vision at 30 cm. What is the power of the inserts?

In the normal eye the ciliary muscles that control the lens will relax:

Glaucoma occurs because:

The eye changes its f-number by:

A person has a near point of 40 cm and a far point of 2.0 m. When looking through lenses of focal length -2.0 m, what is the nearest an object can be to be seen clearly?

The "normal" eye has a near point of 25 cm.If a given individual's near point is 73 cm, for what problem will the eye doctor prescribe correction?