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प्रश्न
Give scientific reason:
We cannot clearly see an object kept at a distance less than 25 cm from the eye.
उत्तर
- The muscles attached to the eye lens (ciliary muscles) help in fine adjustments of the focal length of the lens.
- The capacity of these muscles to contract or relax to adjust the focal length (i.e., power of accommodation) has a limit.
- The minimum distance of an object from a normal eye for which the eye lens can decrease its focal length to the least possible value, is 25 cm.
Hence, we cannot clearly see an object kept at a distance less than 25 cm from the eye.
संबंधित प्रश्न
Write short notes on the following: Retina
Explain, why a normal eye is not able to see distinctly the objects placed closer than 25 cm, without putting any strain on the eye.
Where is the image formed in a human eye?
Name the part of the retina which is insensitive to light.
What is the principal function of the eye-lens?
What is the least distance of distinct vision for a normal human eye?
Name the part of our eyes which helps us to focus near and distant objects in quick succession.
Give the scientific names of the following parts of the eye:
a hole in the middle of the iris.
Fill in the following blank with suitable word:
Most of the refraction of light rays entering the eye occurs at the outer surface of the.............
What changes take place in the shape of eye-lens:
when the eye is focused on a distant object?
What are rods and cones in the retina of an eye? Why is our night vision relatively poor compared to the night vision of an owl?
Refraction of light in the eye occurs at:
(a) the lens only
(b) the cornea only
(c) both the cornea and the lens
(d) the pupil
Suggest how your irises help to protect the retinas of your eyes from damage by bright light.
Why does the eye-lens not have to do all the work of converging incoming light rays?
After testing the eyes of a child, the optician has prescribed the following lenses for his spectacles:
Left eye : + 2.00 D
Right eye : + 2.25 D
The child is suffering from the defect of vision called:
(a) short-sightedness
(b) long-sightedness
(c) cataract
(d) presbyopia
Out of animals of prey and predators, which have their eyes:
at the front of their head?
State whether the following statement is true or false:
Rabbit has eyes which look sideways.
The animals called predators have:
(a) both the eyes on the sides
(b) one eye on the side and one at the front
(c) one eye on the front and one at the back
(d) both the eyes at the front
Note the relationship between the first two words and suggest the suitable word/words for the fourth place.
Cones : Iodopsim :: Rods : ______.
Differentiate between members of the following pair with reference to what is asked in bracket.
Rod and cone cells (pigment contained)
With reference to the functioning of the eye, answer the question that follow:
What is the shape of the lens during near vision?
With reference to the functioning of the eye, answer the question that follow:
What is the shape of the lens during distant vision?
Choose the correct answer.
Which one is the photoreceptor _____________
What is meant by power of accommodation of the eye?
Name the following:
The focal length of the lens is altered by the contraction of which type of muscles.
Name the following:
The part of the eye responsible for change in the size of the pupil.
Give Technical Term:
The adjustment of the eye in order to obtain a clear vision of objects at different distances
State the Function:
Visual purple
Complete the following sentence with appropriate Word
The aperture in the eye through which light enters is the:
Draw the struture of human eye and label its parts.
When light rays enter the eye, most of the refraction occurs at the ____________.
We cannot distinguish colours in dim light. Explain giving suitable reasons.
Name the part of the eye which gives colour to the eyes.
What kind of lens is there in our eyes? Where does it form the image of an object?
Which part of the eye gets affected if someone is suffering from cataract? How is it treated?
Match the following:
| Column - I | Column - II |
| 1. Retina | a. Pathway 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 | f. Power of accommodation |
Chris was watching the display of fireworks in the sky.
- Trace the path of the light rays using the following terms:
Fovea, Lens, Conjunctiva, Pupil, Cornea. - Name the nerve that carries the impulse for vision to the brain.
Match the terms in column I with those in column II and write down the matching pairs.
| Column I | Column II | ||
| (i) | Conjunctiva | (a) | Viral infection |
| (ii) | Cornea | (b) | Ciliary body |
| (iii) | Choroid | (c) | Spiral-shaped |
| (iv) | Cochlea | (d) | Transparent epithelium |
| (v) | Conjunctivitis | (e) | Suspensory ligament |
| (f) | Contains melanin | ||
| (g) | Transparent but appears black |
