Nearsightedness: elongated eyeball : : farsightedness: _______ - Science and Technology 1

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Nearsightedness: elongated eyeball : : farsightedness: _______



Nearsightedness: elongated eyeball : : farsightedness: flattening of eye ball

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Chapter 7: Lenses - Find the correlation.


Given below is a diagram showing a defect of human eye. Study it and answer the following questions.

(i) Name the defect shown in the figure.
(ii) Give reason for this defect of eye in human being.
(iii) Name the type of lens used to correct the eye defect.

In a Std. X class out of 40 students 10 students use spectacles, 2 students have positive power and 8 students have negative power of lenses in their spectacles.

Answer the following questions:

(1) What does the negative power indicate?

(2) What does the positive power indicate?

(3) Generally which type of spectacles do most of the students use?

(4) What defect of eyesight do most of the students suffer from?

(5) Give two possible reasons for the above defect.

What is myopia?

Explain two possible reasons of myopia. How can it be corrected? Explain with a suitable diagram.

The kind of lens required to correct Myopia

Which defect of vision can be rectified: 

 by using a convex lens?

What is the other name for 


Where is the near point of a person suffering from hypermetropia (or long-sightedness)?

A man can read the number of a distant but clearly but he finds difficulty in reading a book.  

What type of spectacle lens should he use to correct the  defect?

A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard. 

 Name the type of defect he is suffering from.

A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard. 

 How can this defect by corrected?

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.

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.

A short-sighted person has a near point of 15 cm and a far point of 40 cm.
(a) Can he see clearly an object at a distance of:
(i) 5 cm?
(ii) 25 cm?
(iii) 50 cm?
(b) To see clearly an object at infinity, what kind of spectacle lenses does he need?

What is meant by optical illusion? Give one example.

Given below is a diagram depicting a defect of the human eye. Study the same and answer the question that follow:

Name the defect shown in the diagram.

Observer the following diagram and answer the questions.
a) Which eye defect is shown in this diagram?
b) What are the possible reasons for this eye defect?
c) How this defect is corrected, write it in brief?

State the main functions of the following: 

Name the following:
The photosensitive pigment present in the rod cells of the retina.

Distinguish between the following pair of words:
Myopia and hypermetropia

Why does one feel blinded for a short while on coming out of a dark room?

The diagram alongside represents a section of a mammalian eye.
(i) Label the parts 1 to 5 of the diagram.
(ii) State the function of the parts labelled 4 and 5.
(iii) With the help of a diagram show the short sightedness.

Name the cells of the retina that are sensitive to colours.

Choose the correct answer : 
Presbyopia is a disease of _____________

Rewrite the following table so as to match second and third column with first column.


Column I
Column II
Column III
(i) Myopia
Old age problem
Bifocal lens
(ii) Presbyopia
Concave lens.

Anuja cannot see the blackboard writing but she can see nearby things.
(a) What is the eye defect she is suffering from?
(b) State the possible reason for her defect.
(c) How is it corrected

Give Reason:

Why do we see clearly in the central region of the retina?

Differentiate between:

Myopia and Hypermetropia.

Draw a neat labeled diagram to show how hypermetropia can be rectified.

Explain the Term: Hypermetropia

Explain the Term: Astigmatism

What type of lens is used to correct Hypermetropia?

The diagram given below represents the cross-section of the human eye:

(i) Name the parts labeled 1—12.
(ii) What is the function of the part marked ‘10’?
(iii) What would happen if part ‘5’ is damaged or cut?

In Myopia the human eye _______.

Due to elongation of _______ and increase in curvature of the eye lens, a person cannot see distant objects clearly.

Nearsightedness : concave lens : : farsightedness : _______

Write scientific reason.

Nearsightedness, this defect can be corrected by using spectacles with concave lens.

Observe the given below the figure, correct it and explain and write about the concept depicted in this figure.

Given below is a diagram showing a defect of vision. Name the defect of vision and draw an accurately labelled diagram to correct this defect.

What are the causes of ‘Myopia’?

Differentiate the eye defects: Myopia and Hypermetropia

Assertion: Myopia is the defect of vision in which a person cannot see distant objects clearly.

Reason: This due to eye-ball being too short.

Correlate the given sequence:

Hypermetropia : Convex lens : ______ : Concave lens

Observe the figure whether it is correct or not and explain the phenomenon.

Observe the figure and answer the following questions: 

  1. Name the defect of vision represented in the above figure.
  2. State the reasons for this defect.
  3. How is it corrected?
  4. Draw the diagram to show the correction of this defect.

Match the following:

Column - I Column - II
1. Retina a. Path way of light
2. Pupil b. Far point comes closer
3. Ciliary muscles c. near point moves away
4. Myopia d. Screen of the eye
5. Hypermetropia e. Power of accommodation

Complete the following table by observing the given figure:

Figure →
Points ↓
(a) Name of the defect ____________ ____________
(b) Position of the image ____________ ____________
(c) Lens used to correct the defect ____________ ____________

A teacher drew the diagram of the heart on the blackboard and told the students to copy it in their notebooks. Mahesh couldn't see the diagram clearly as it appeared blurred to him.

  1. Name the defect of the eye Mahesh is suffering from.
  2. Where is the image formed in this defect?
  3. Mahesh consults an eye doctor and is prescribed suitable lenses to correct the defect. Which type of lens do his spectacles have?


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