Give reason for the following:

1) Red light is used for danger signal

2) Cause of Color blindness.

3) Sky appears black in Moon.

4) Rainbow is seen on a rainy day in the presence of sunlight.

4) A person with a myopia eye cannot see objects beyond a distance of 1.5m. What would be the power of corrective lens? Which type of lens is used?

5) What do you understand by myopia? Write two causes of it?

6) What do you mean by far point and near point of eye?

7) What is presbyopia? State the cause of it and how is it corrected?

8) Explain: 1) why does sky look blue on a clear day

2) Twinkling of stars.

9) What is hypermetropia? State two causes of hypermetropia with help of ray diagrams show:

1) The eye defect hyperopia.


1.Why does it takes sometimes to see in a dim room when you enter the room from bright sunlight outside?

ANS: In the bright iris causes the pupil to become smaller so that only a small portion of light enter the eye and rods of the retina are also adjusted in the same way. but when a person enter in to dim lighteach iris takes sometimes to increase the diameter of the pupil so that more amount of light can enter the eyes to see the objects clearly and rods of the retina also takes some time to adjust –themselves to get the picture of the object in the dim light.

2Can we see a rainbow on the moon?

ANS:No, since there is no atmosphere on the moon.

3.Does a beam of light give a spectum on passing through a hollow prism?

ANS:No,this is because dispersion of light cannot occur through a hollow prism containing air.



1. Name the place where image is formed in the eye?

2. Name the muscular diaphragm that controls the size of the pupil.

3. What is the cause of dispersion of light?

4. Give the cause of cataract of eye.

5. Which color has got more wavelength?

6. What makes bees respond to ultraviolet light?


1) What is the focal length of a plane mirror?

2) Which of the two has a great power, a lens of shot focal lenth or a lens of large length?

3) What does m= +1 stand for?

4) What is the power of a lens if its focal lenth is 50cm?

5) What is the nature of image at retina?

6) Name the point inside the lens through which a ray of light goes deviated?

7) What is the S.I. unit of power of a lens?

Home Assignment

1. Name the photographic film equivalent to our eye .

2.Why does a glass slab not disperse white light?

3.Why do we not perceive the depth of a lake ?

4.Name two causes of Myopia, Hypermetropia and presbiopia.

5.Name the liquids that keep our eye soft.

6.What causes rainbow formation?

7.What is Mirage?

Project work:

1) To understand the dispersion of light with help of activity?

(Hint: materials, an irregularly shaped glass, white screen).

2) List, observe, reason and explain three cases of nature where dispersion happens.

(hint: 1) Sun rise and sun set 2.Formation of rainbow.3.Twinkling of stars)

3) Draw a labeled diagram of human eye and explain the function of retina, cornea, pupil, rods, and cones?

seminar: (students will be divided into groups 7 they will present papers on the topic)


2) Means to overcome and Corrective measure

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