Power of Accommodation

Q.

Question 9
What happens to the image distance when we increase the distance of an object from the eye?

Q.

A person needs a lens of power $-5.5dioptres$ for correcting his distant vision. For correcting his near vision he needs a lens of power $+1.5dioptre$. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?

Q.

Question 2
A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?

Q. Question 8
Why is a normal eye not able to see clearly the objects placed closer than 25 cm?

Q.

The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct this defect? (Assuming that the near point of a normal eye is 25 cm)

1. +3 D

2. - 3 D

3. +4 D

4. -4 D

Q.

A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his textbook. Which of the following statements is correct?

1. The near point of his eyes has receded away

2. The near point of his eyes has come closer to him

3. The far point of his eyes has come closer to him

4. The far point of his eyes has receded away

Q. Question 4
A student has difficulty in reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?

Q. In our eye, if the convex lens produces a inverted image on a retina then how do wee see the erect image of a person?

Q.

What changes the shape of lens in the eye ?

Q.

Define the term power of accommodation. Write the modification in the curvature of the eye lens which enables us to see the nearby objects clearly.

Q.

The human eye can focus on objects at different distances by adjusting the focal length of the eye lens. This is due to:

1. presbyopia
2. accommodation
3. far-sightedness
4. near-sightedness

Q. Due to gradual weakening of ciliary muscles and diminishing flexibility of the lens a certain defect of vision arises. Write the name of this defect . Name the type of lens required by such persons to remove the vision. Explain the structure and function of such a lens.

Q.

Ciliary muscles are responsible for changing the focal length of the eye lens according to the distance of the object.

1. True

2. False

Q. What changes take place in the shape of eye-lens :
(a) when the eye is focused on a near object ?
(b) when the eye is focused on a distant object ?

Q. The ability of eye lens to adjust its focal length is called

1. presbyopia
2. accommodation
3. myopia
4. hypermetropia

Q.

The curvature of the eye lens can be modified by

1. retina

2. ciliary muscles

3. cornea

4. pupil

Q.

Derive the formula to calculate the focal length of a lens used for correcting a myopic eye.

Q. A person is unable to see the objects placed beyond 2.5 m clearly. What is the defect of vision he is suffering from? Suggest a corrective lens for his defect.

1. Hypermetropia, concave lens
2. Myopia, concave lens
3. Hypermetropia, convex lens
4. Myopia, convex lens

Q.

What is the shape of the lens during (1) near vision, (2) distant vision?

Q.

The ability of the eye to see objects at all distances is called

Q. Why do we need two eyes not a one eye?

Q.

What are the properties of image formed on the retina of the eye?

1. real and straight

2. imaginary and inverted

3. imaginary and straight

4. real and inverted

Q.

Why is a normal eye not able to see clearly the objects placed closer than 25cm? [3 MARKS]

Q. The term "accommodation" as applied to the eye, referes to its ability to :
(a) control the light intensity falling on the retina
(b) erect the inverted image formed on the retina
(c) vary the focal length of the lens
(d) vary the distance between the lens and retina

Q. The ability of an eye lens to adjust its focal length to form sharp images on the retina is known as its power of accommodation.

1. True
2. False

Q. The human eye possesses the power of accommodation. This is the power to :
(a) alter the diameter of the pupil as the intensity of light changes
(b) distinguish between lights of different colours
(c) focus on objects at different distances
(d) decide which of the two objects is closer.

Q.

When does the focal length of the eyes increase?

Q.

The ciliary muscles in an eye change the focal length of an eye lens to focus distant or nearby objects clearly, this ability of an eye is known as the power of an eye.

1. True
2. False

Q. If your eye glasses have focal length +60 cm, what is your near point?

Q. Where is the image formed when the object is at the near point of the eye?