CBSE Guess > Papers > Question Papers > Class X > 2008 >Science > Science Theory Ans. 2nd period → Li Be B C N O F (b) Most metallic element is Li, most non-metallic element is F. On moving from left to right in a periodic table the metallic character of elements decreases but the non-metallic character increases. Metals lose electrons and form positive ions so metals are electropositive whereas non-metals accept electrons and form negative ions, so nonmetals are electronegative.On moving from left to right in a period the nuclear charge (positive) increases as the number of protons increases, therefore the valence electrons are pulled in more strongly by the nucleus so the tendency of atoms to lose electrons decreases. Q. 11. A convex lens has a focal length of 10 cm. At what distance from the lens should the object be placed so that it forms a real and inverted image 20 cm away from the lens? What would be the size of the image formed if the object is 2 cm high? With the help of a ray diagram show the formation of the image by the lens in this case. Sol. Focal length of the convex lens, f = + 10 cm
CBSE 2008 Question Papers Class X
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