Q30 of 30 Page 1

(i) A lens produces a magnification of -0.5. Is this a converging or diverging lens? If the focal length of the lens is 6 cm, draw a ray diagram showing the image formation in this case.

(ii) A girl was playing with a thin beam of light from a laser torch by directing it from different directions on a convex lens held vertically. She was surprised to see that in a particular direction, the beam of light continues to move along the same direction after passing through the lens. State the reason for her observation. Draw a ray diagram to support your answer.


OR


(i) On entering in a medium from air, the speed of light becomes half of its value in air. Find the refractive index of that medium with respect to air?


(ii) A glass slab made of a material of refractive index n1 is kept in a medium of refractive index n2.


A light ray is incident on the slab. Draw the path of the rays of light emerging from the glass slab, if (i) n1> n2 (ii) n1 = n2 (iii) n1< n2


(i) When a convex or converging lens forms a real image, the magnification is considered negative. This is so because the image is inverted.



(ii)


When the beam of light passes through the optic center, the ray shouldn’t deviate. Here when the girl was playing with the laser beam with convex lens placed vertically, the ray must be passing through the optical center.



The reason being that the middle part of a lens is like a thin glass slab, so almost no deviation takes place and very slight lateral displacement of the incident ray takes place.


OR


(i)


We know from Snell’s law; refractive index of a medium is given by-



Where,


n = refractive index


c=speed of light in vacuum


v=speed of light in medium


In medium, speed of light becomes 1/2


So refractive index becomes,



(ii)


Given


Refractive index of slab = n1


Refractive index of medium = n2



(i)When n1> n2, the incident ray bends away from the normal of glass slab as shown in fig. below



(ii) When n1 = n2, there won’t be any refraction



(iii)When n1< n2, the ray of light will bend towards the normal as shown in fig. below.



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26

The formulae of four organic compounds are given below:


(i) Which one of these compounds A, B, C or D is a saturated hydrocarbon?


(ii) Identify the organic acid and give its structural formula.


(iii) Which ofthe above compounds when heated at 443K in the presence of concentrated forms ethene as the major product? What is the role played byconcentrated in this reaction? Also write the chemical equationinvolved.


(iv) Give a chemical equation when B and C react with each other


in presence of concentrated. Name the major product formed andmention one of its important use.


 27


(i) Identify any two parts from the above diagram which carry oxygenated and deoxygenated blood.


(ii) Explain the process of double circulation with the help of a flow chart


 28

(i) Describe the various steps involved in the process of binary fission with the help of a diagram.

(ii) Why do multicellular organisms use complex way of reproduction?


OR


(i) Describe the role of prostate gland, seminal vesicle and testes in the human male reproductive system.


(ii) How is the surgical removal of unwanted pregnancies misused?


(iii) Explain the role of oral contraceptive pills in preventing conception.


 29

(i) Consider a conductor of resistance ‘R’, length ‘L’, thickness’ d’ and resistivity ‘ρ’. Now this conductor is cut into four equal parts. What will be the new resistivity of each of these parts? Why?

(ii) Find the resistance if all of these parts are connected in:


(a) Parallel


(b) Series


(iii) Out of the combinations of resistors mentioned above in the previous part, for a given voltage which combination will consume more power and why?