A student wants to project the image of a candle flame on a screen 90 cm in front of a mirror by keeping the flame at a distance of 15 cm from its pole.

(a) Suggest the type of mirror he should use.

(b) Determine the liner magnification in this case.

(c) Find the distance between the object and its image.

(d) Draw ray diagram to show the image formation in this case.

The elements Be, Mg and Ca each having two electrons in their outermost shells are in periods 2, 3, and 4 respectively of the modern periodic table.

Answer the following questions, giving justification in each case:

(i) Write the group to which these elements belong.

(ii) Name the least reactive element.

(iii) Name the element having largest atomic radius.

Define the term 'structural isomerism'. Explain why propane cannot exhibit this property. Draw the structures of possible isomers of butane, C₄H₁₀

Write one difference between asexual and sexual mode of reproduction. Which species is likely to have better chances of survival-the one reproducing asexually or the one reproducing sexually?

Justify your answer.

What is the effect of DNA copying, which is not perfectly accurate, on the reproduction process? How does the amount of DNA remain constant though each new generation is a combination of DNA copies of two individuals?