Q29 of 30 Page 1

(a) A security mirror used in a big showroom has radius of curvature 5 m. If a customer is standing at a distance of 20, from the cash counter, find the position, nature and size of the image formed in the security mirror.

(b) Neha visited a dentist in his clinic. She observed that the dentist was holding an instrument fitted with a mirror. State the nature of this mirror and reason for its use in the instrument used by dentist.


OR


Rishi went to a palmist to show his palm. The palmist used a special lens for this purpose.


(i) State the nature of the lens and reasons for its use.


(ii) Where should the palmist place/hold the lens so as to have a real and magnified image of an object?


(iii) If the focal length of this lens is 10 cm, the lens is held at a distance of 5 cm from the palm, use lens formula to fine the position and size of the image.


(a) The focal length of the convex mirror is 2.5 m


The customer is 20 m away from the mirror, u = -20 m (as per sign convention)


Using lens formula



Show the image will be formed at a distance of 20/9 m.; the image will be diminished, virtual and erect.


(b) Concave mirrors are used as they converge the reflecting light at the focus. Also the object kept at a distance less than the focal length of the mirror produces enlarged, erect and virtual images of the object; which enables the doctor to clearly see the image of the tooth or the part of the mouth that is being inspected.


OR


(i) Convex lens is used by the palmist to get an enlarged image of the palm revealing the details even more clearly for him when placed real close to the object.


(ii) There are two cases for which a real and magnified image of object is obtained in convex lens-


a. When the object is placed at the focus of the lens.


b. When the object is placed between F and 2F of the lens.


(iii) f= 10


u = - 5


By lens formula



v = -10 cm


The size of the image will be,



The height of the image is twice that of the object.


More from this chapter

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26

A metal ‘M’ is stored under kerosene. It vigorously catches fire, if a small piece of this metal is kept open in air. Dissolution of this metal in eater release great amount of energy and the metal catches fire. The solution so formed turns red litmus blue.

(a) Name the metal ‘M’


(b) write formula of the compound formed when this metal is exposed to air.


(c) Why is metal ‘M’ stored under kerosene?


(d) If oxide of this metal is treated with hydrochloric acid, what would be the products?


(e) Write balanced equations for:


(i) Reaction of ‘M’ with air.


(ii) Reaction of ‘M’ with water.


(iii) Reaction of metal oxide with hydrochloric acid.


OR


(a) Write electro dot structures of Ca (At. No. 20) and O (At. No. 8).


(b) Show the formation of calcium oxide by transfer of electrons.


(c) Name the ions present in the compound.


(d) List four important characteristics of this compound.


 27

Write the correct sequence of steps followed during journey of oxygen rich blood from lungs to various organs of human body.

(b) What happens when the system of blood vessels develop a leak?


 28

(a) Suggest any two categories of contraceptive methods to control the size of human population which is essential for the prosperity of a country. Also explain about each method briefly.

(b) Name two bacterial and two viral infections each that can get sexually transmitted.


(c) List two advantages of using condom during sexual acct.


OR


(a) Draw a diagram to show spore formation in Rhizopus.


(b) With the help of an example differentiate between the process of Budding and Fragmentation.


(c) Why is vegetative propagation practiced for growing some type of plants?


 30

(a) An electric bulb is rated at 200 V; 100 W. What is its resistance?

(b) Calculate the energy consumed by 3 such bulbs if they glow continuously for 10 hours for complete month of November.


(c) Calculate the total cost if the rate is Rs. 6.50 per unit.


OR


(a) What is meant by the statement, “The resistance of conductor is one ohm”?


(b) Define electric power. Write an expression relating electric power potential difference and resistance.


(c) How many 132 Ω resistors in parallel par required to carry 5 A on a 220 V line?