Myopia and Its Correction

Q.

What type of lens is used to correct (a) hypermetropia (b) myopia?

Q.

Myopic eye defect can be corrected by using convex lens.

1. True

2. False

Q.

List five differences between myopia and hypermetropia.

Q.

The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?

Q.

What is the reason for the occurence of hypermetropic defect?

1. Excessive curvature of eye lens

2. Elongation of the eye ball

3. Shortening of eye ball

4. Both a and b

Q.

What is the last digit of $6^{100}$?

Q. What are the two most common defects of vision (or defects of eye) ? How are they corrected ?

Q. (a) What is short-sightedness ? State the two causes of short-sightedness (or myopia). With the help of ray diagrams, show :
(i) the eye-defect short-sightedness.
(ii) correction of short-sightedness by using a lens.
(b) A person having short-sight cannot see objects clearly beyond a distance of 1.5 m. What would be the nature and power of the corrective lens to restore proper vision ?

Q.

Convex mirrors are used as side mirrors in automobiles. Explain their working.

Q.

What signs for object distance and image distance must we take for a myopic eye and a hypermetropic eye?

Q.

The far point of a myopic eye is 20 cm . Find the power of his lens used.

1. 3D

2. -3D

3. 5D

4. -5D

Q. Explain with the help of labelled ray diagram, the defect of vision called myopia and how it is corrected by a lens.

Q.

Question 17
A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?

Q.

Name the type of mirror which is used as a rear-view mirror in a car. Give a reason.

Q. A person cannot see distant objects clearly. His vision can be corrected by using the spectacles containing :
(a) concave lenses (b) plane lenses (c) contact lenses (d) convex lenses

Q.

State whether the following statements are true or false.

1. Hypermetropia is a defect of eye caused due to the eyeball being elongated.

1. True
2. False

Q. A person suffering from the eye-defect myopia (short-sightedness) can see clearly only up to a distance of 2 metres. What is the nature and power of lens required to rectify this defect ?

Q. A person got his eyes tested. The optician's prescription for the spectacles reads :
Left eye : - 3.00 D Right eye : - 3.50 D
The person is having a defect of vision called :
(a) presbyopia (b) myopia (c) astigmatism (d) hypermetropia

Q. Statement1: Myopia is corrected by the use of the concave lens.
Statement 2: A concave lens forms a virtual image of the object kept at infinity at its focus. Therefore the image formed by concave lies within the far point of the myopic eye, which then acts as the object for the myopic eye thus helping it view it.

1. Both statements are wrong.
2. Statement 1 is correct but statement 2 is incorrect.
3. Statement 1 and 2 are correct but statement 2 is not the reason for statement 1.
4. Statement 1 and 2 are correct and statement 2 is the correct reason for statement 1.

Q. If a person is wearing concave lens, then what defect of vision is he suffering from?

1. Astigmatism
2. Presbyopia
3. Myopia
4. Cataract

Q. A student sitting on the last bench in the class cannot read the writing on the blackboard clearly but he can read the book lying on his desk clearly. Which of the following statement is correct about the student ?
(a) The near point of his eyes has receded away.
(b) The near point of his eyes has come closer to him.
(c) The far point of his eyes has receded away.
(d) The far point of his eyes has come closer to him.

Q. Name the defect of vision which can be corrected by a diverging lens. Show clearly by a ray diagram how the lens corrects the defect.

Q.

When light undergoes refraction at the surface of separation of two media, what happens to its wavelength?

Q. What is the far point of a person suffering from myopia (or long-sightedness) ?

Q. Complete the following sentences :
(a) A short-sighted person cannot see .............. objects clearly. Short-sightedness can be corrected by using ............... lenses.
(b) A long-sighted person cannot see ............... objects clearly. Long-sightedness can be corrected by using .............. lenses.

Q. A person cannot see the distant objects clearly (though he can see the nearby objects clearly). He is suffering from the defect of vision called :
(a) cataract (b) hypermetropia (c) myopia (d) presbyopia

Q. Assertion : Optical fibres are used for telecommunication.
Reason : Optical fibres are based on the phenomenon of total internal reflection.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
2. Assertion is correct but Reason is incorrect.
3. Both Assertion and Reason are incorrect.
4. Both Assertion and Reason are correct and but Reason is not the correct explanation for Assertion.

Q. A person wears a pair of spectacles with a concave lens of power -2D. Find the farthest point to which he can see objects distinctly without his spectacles.

1. 25 cm
2. 30 cm
3. 50 cm
4. 20 cm

Q. Name one of the common defects of vision and the type of lens used to remove it.

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?