Q4 of 102 Page 127

Give the reason for the following:

(i) Medicines dropped in the eye flow down into the nose ___________________


(ii) A person from bright sunlight outside enters a poorly lit room and feels blinded for a short while ___________________

(i) When medicine is dropped into the eyes, it passes into the back of the nose via the lacrimal punctum that leads to the nasolacrimal duct. This is the duct that connects the nose to the eyes.


 



 


(ii) When one enters a dim lit room with bright sunlight, it takes some time to see the objects. This is due to the fact that in bright sunlight the pupil of our eye is in the contracted form. So, when we enter the dim lit room, very little light enters our eye and we are unable to see properly. After a short time, the pupil of our eye expands or dilates and becomes large. Regeneration of rhodopsin leads to more light then entering the eye and we can see clearly.


 

More from this chapter

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2

Write in proper sequence the names of all the parts of the human eye through which the light rays coming from an object pass before they form an image on the retina.

 3

Name the following:

(i) Place of best vision in the retina of the eye __________________


(ii) Place of no vision in the retina of the eye __________________


(iii) Kind of retinal cells sensitive to dim light __________________


(iv) The circular opening enclosed by iris __________________


(v) The fibers which collectively hold the lens in position __________________


(vi) The capacity of the eye to focus at different distances __________________


(vii) The kind of lens required to correct nearsightedness __________________


(viii) The layer of the wall of the eye-ball that corresponds to the black lining of the box of a camera __________________

 1

Categorize the following parts under

(i) External ear: _________________


(ii) Middle ear: _________________


(iii) internal ear: _________________


Eardrum, hammer, pinna, cochlea, anvil, stirrup, Eustachian tube, tympanum, oval window, semi-circular canals.

 2

State the functions of the following: -

(a) Semi-circular canals _____________


(b) Cochlea _____________


(c) Auditory nerve _____________