Q24 of 58 Page 1

(a) Write the function of each of the following parts of human eye:

cornea; iris; crystalline lens; ciliary muscles


(b) Millions of people of the developing countries of the world are suffering from corneal blindness. These persons can be cured by replacing the defective cornea with the cornea of a donated eye. A charitable society of your city has organize a campaign in your neighbourhood in order to create awareness about this fact. you are asked to participate in this mission how would you contribute in noble cause?


(i) State the objective of organizing such campaigns.


(ii) List two arguments which you would give to motivate the people to do their eyes after death.


(iii) List two value which are developed in the persons who actively participate and contribute in such programmes.

(a) Functions of the following parts of human eye:


(i) Cornea- The front part of the eye is called cornea. Most of the refraction for the light rays entering the eye occurs at the surface of the cornea.


(ii) Iris- This is a flat, colored, ring-shaped membrane behind the cornea. It controls the size of the pupil.


(iii) Crystalline lens- Eye lens is a convex lens which focuses the image of the on the retina.


(iv) Ciliary muscles- Ciliary muscles hold the eye lens and changes the this eye-lens while focusing. When these muscles are relaxed the lens becomes thin. Thus, its focal length increases. This enables us to see distant objects clearly. While looking at the closer objects these muscles contract. This increases the curvature of the eye lens, it becomes thick. With this focal length decreases and we see nearby objects clearly.


(b) (i) Objective of such campaigns. To make people aware of corneal blindness make them realize their duties towards the society by taking pledge of donation.


(ii) One pair of eyes can give eyesight to two corneal blind persons (each one eye), and make them see this beautiful world.


(iii) Values developed in persons who actively participate in such programmes are social welfare and awareness.


Note: Our eyes can live even after our death. People belonging to all age groups, even people with medical conditions like cataract, diabetes, hypertension can donate their eyes.


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22

(a) Define the following terms in the context of spherical mirrors:

(i) Pole (ii) Centre of curvature


(iii) Principal axis (iv) Principal focus


(b) Draw ray diagrams to show the principal focus of a:


(i) Concave mirror (ii) Convex mirror


(c) Consider the following diagram in which M is a mirror and P is an object and Q


Is its magnified image formed by the mirror?



State the type of the mirror M and one characteristic property of the image Q.

 23

(a) Draw a ray diagram to show the formation of image by a convex lens when an object is placed in front of the lens between its optical centre and principal focus.

(b) In the above ray diagram mark the object-distance (u) and the image-distance (v) with their proper signs (+ve or -ve as per the new Cartesian sign convention) and state how these distances are related to the focal length (f) of the convex lens in this case.


(c) Find the power of a convex lens which forms a real, and inverted image of magnification -1 of an object placed at a distance of 20 cm from its optical centre.

 25

Which of the following sets of materials can be used for conducting a saponification reaction for the preparation of soap?

 26

A student takes four test tubes marked P, Q R and S of 25 mL capacity and fills 10 mL of distilled water in each. He dissolves one spoon full of four different salts in each as-KCl in P, NaCl in Q CaCI2 in Rand MgCI2 in S. He then adds about 2 mL of a sample of soap solution to each of the above test tubes. On shaking the contents of each of the test tubes, he is likely to observe a good amount of lather (foam) in the test tubes marked: