Q24 of 30 Page 1

(a) With the help of labelled ray diagram show the path followed by a narrow beam of monochromatic light when it passes through a glass prism.

(b) What would happen if this beam is replaced by a narrow beam of white light?


OR


(a) A person is suffering from both myopia and hypermetropia.


(i) What kind of lenses can correct this defect?


(ii) How are these lenses prepared?


(b) A person needs a lens of power + 3D for correcting his near vision and – 3D for correcting his distant vision. Calculate the focal lengths of the lenses required to correct these defects.


(a) In the case of monochromatic light the ray will bend due to refraction but it will not show dispersion of light.


(b) When a white beam of light is allowed to pass through the prism, it will get dispersed into its 7 colours component of spectrum of light. The splitting of light into its component colours is called dispersion.


The following diagram show the phenomena: -



OR


(a)(i) A person suffering from both myopia and hypermetropia at the same time requires a spectacle consisting of both concave and convex lens of prescribed focal length.


(ii) It is prepared by setting half the lens of the spectacle to be concave and the remainder half to be a convex type lens.


(b) The power of the lens is defined as the reciprocal of the focal length. It is a measure of the ability of the lens to focus.


Mathematically, it can be described as,



The power of the lens is + 3 D




The power of the lens is - 3 D




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22

The diagram given below show an Object O and its image I.


Without actually drawing the ray diagram, state the following:


(i) Type of lens (Converging / Diverging)


(ii) Name two optical instruments where such an image is obtained.


(iii) List three characteristics of the image formed if this lens is replaced by a concave mirror of focal length 'f and an object is placed at a distance 'f/2' in front of the mirror.


 23

Give reasons for the following:

(i) There is either a convergence or a divergence of magnetic field lines near the ends of a current carrying straight solenoid.


(ii) The current carrying solenoid when suspended freely rests along a particular direction.


(iii) The burnt out fuse should be replaced by another fuse of identical rating.


 25

Write balanced chemical equations to explain what happens, when

(i) Mercuric oxide is heated.


(ii) Mixture of cuprous oxide and cuprous sulphide is heated.


(iii) Aluminium is reacted with manganese dioxide.


(iv) Ferric oxide is reduced with aluminium.


(v) Zinc carbonate undergoes calcination.


OR


(i) By the transfer of electrons, illustrate the formation of bond in magnesium chloride and identify the ions present in this compound.


(ii) Ionic compounds are solids. Give reasons.


(iii) With the help of a labelled diagram show the experimental set up of action of steam on a metal.


 26

(a) Compare soaps and detergents on the basis of their composition and cleansing action in hard water.

(b) What happens when ethanol is treated with sodium metal? State about the behaviour of ethanol in this reaction.


(c) Draw the structure of cyclohexane.


(d) Name the following compound