Question

the draft constitution is. a document. which SPR SCHOOL OF EXCELLENCE

Yellapur, Warangal

1. What is the function of lens in human eye?

Ans. The lens in human eye is responsible for image formation on retina by

converging the light rays which are coming from the object.

2. What is the role (or function) of ciliary muscle in our eye?

Ans. 1) Ciliary muscles are useful to see distant as well as closer objects clearly.

2) The ciliary muscle to which eye lens is attached helps to change focal length of

eye lens by changing radii of curvature of eye lens.

3) When the eye is focused on a distant object, the ciliary muscles are relaxed so that

the focal length of eye lens has its maximum value which is equal to its distance

from the retina.

4) When the eye is focussed on a closer object the ciliary muscles are strained and

focal length of lens decreases.

5) The ciliary muscles adjust the focal length in such a way that the image is formed

on retina.

6) The rays coming into the eye are focussed on the retina then we can see the object

clearly.

7) This process of adjusting focal length is called accommodation.

3. A person is viewing an extended object. If a converging lens is placed in front of

his eye, will he feel that the size of object has increased? Why?

Ans. 1) The person feels that the size of object has increased.

2) He used the converging lens, i.e., the convex lens in air and the object is an

extended object.

3) If this object is placed in between focus(F) and optic centre (O) of the lens, the

formed image will be virtual, erect and magnified.

4) Hence the image size seems to be increased.

4. Light of wavelength(λ1) enters a medium with refractive index n2

from a

medium with refractive index n1

. What is the wavelength of light in second

medium ?

Absolute refractive index =

But we know that where ν is the frequency of light

⇒ ; ⇒ (Since in refraction C and ν are constants)

5. How does ciliary muscle help to see objects at long distances and short

distances?

Ans. Ciliary muscles help to see objects at long distances and short distances by a

process of adjusting focal length of eye lens. This process is called "Accomodation".

6. How is it possible to get the image at the same distance on the retina for various

object distances?

Ans. The distance between the lens and retina is about 2.5 cm i.e., for any position of

object in front of the eye the image distance is fixed and about 2.5 cm and its

possible by adjusting the radii of curvature (i.e., focal length) of the eye lens done by

ciliary muscles to which eye lens is attached.

7. How do you find least distance of distinct vision experimentally?

Ans.

1. Hold the text book at certain distance with our hands. Try to read the content on

the page.

2. Gradually move the books towards eye, till it reaches very close to our eyes. we

may see that printed letters on the page appear blurred or we will feel strain to read.

3. Now move the book backwards to a position where we can see clear printed letters

without strain. Now measure distance between our eye and text book at this position.

Note down its value.

4. Repeat this activity with other healthy adults and note down the distances for

distinct vision in each case.

5. Find the average of all these distances of clear vision. We notice that we can see

an object comfortably and distinctly at a distance about 25cm from our eyes. This

25cm distance is called least distance of distinct vision.

6. This value varies from person to person and with age.

8. How can you find angle of vision experimentally ? (Or) What is maximum angle

at eye, a person can able to see whole object ? Write an activity to find that

angle.

Ans. Angle of vision: The maximum angle, at which we are able to see the whole

object is called angle of vision.

Experiment to find angle of vision:

Aim: To find angle of vision

HUMAN EYE AND COLOURFUL WORLD​

Answer 1

Answer:

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