Advertisements
Advertisements
प्रश्न
Give Reason:
Deficiency of vitamin A causes night blindness.
Advertisements
उत्तर
Because the visual purple (Rhodopsin) of the rods is not formed in the absence of vitamin A.
APPEARS IN
संबंधित प्रश्न
Write the importance of ciliary muscles in the human eye. Name the defect of vision that arises due to gradual weakening of the ciliary muscles. What types of lenses are required by the person suffering from this defect to see the objects clearly?
Akshay, sitting in the last row in his class, could not see clearly the words write on the blackboard. When the teacher noticed it, he announced if any student sitting in the front row could volunteer to exchange his seat with Akshay. Salman immediately agreed to exchange his seat with Akshay. He could now see the words written on the blackboard clearly. The teacher thought it fit to send the message to Akshay’s parents advising them to get his eyesight checked.
In the context of the above event, answer the following questions:-
(a) Which defect of vision is Akshay suffering from? Which type of lens is used to correct this defect?
(b) State the values displayed by the teacher and Salman.
(c) In your opinion, in what way can Akshay express his gratitude towards the teacher and Salman?
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?
Explain with the help of labelled ray diagram, the defect of vision called myopia and how it is corrected by a lens.
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 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 a young man
Choose the correct answer :
Presbyopia is a disease of _____________
Name the common defects of the eye.
Name an old age eye defect. Why is it caused?
Give Reason:
When you enter into a dark room from bright because of sunlight, you can not see things for a few seconds.
When do we consider a person to be myopic or hypermetropic? Explain using diagrams how the defects associated with myopic and hypermetropic eye can be corrected?
