Advertisements
Advertisements
Question
A person can read a book clearly only if he holds it at an arm's length from him. Name the defect of vision:
if the person is an old man
Advertisements
Solution
If the person is an old man, then the defect of vision is presbyopia. It usually occurs in old age when a person cannot see nearby objects clearly because of the loss of the eye's power of accommodation.
APPEARS IN
RELATED QUESTIONS
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 the other name for
myopia
What is the other name for
hypermetropia
What is the scientific name of
short-sightedness
Name any two defects of vision which can be corrected by using spectacles.
The near-point of a person suffering from hypermetropia is at 50 cm from his eye. What is the nature and power of the lens needed to correct this defect? (Assume that the near-point of the normal eye is 25 cm).
A person is unable to read a book placed closer than 1 meter from his eyes. Identify the defect of vision in his eyes. Draw the ray diagrams to show the defect of vision and its correction.
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?
State the main functions of the following:
Tears
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Draw a labeled diagram to show how the above mentioned defect is rectified using the lens named above.
Give Reason:
Why do we see clearly in the central region of the retina?
Give Reason:
Deficiency of vitamin A causes night blindness.
Give Reason:
When you enter into a dark room from bright because of sunlight, you can not see things for a few seconds.
Choose the Odd One Out:
Nearsightedness : concave lens : : farsightedness : _______
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.
Draw ray diagram showing myopic eye.
Correlate the given sequence:
Hypermetropia : Convex lens : ______ : Concave lens
Observe the following diagram and answer questions following it:
- Identify the defect of vision shown.
- List its two causes.
- Name the type of lens used for the correction of this defect.
