An object of height 5 cm placed perpendicular to the principal axis of a concave lens of focal length 10 cm. H the distance of the object from the optical center is 20 cm. determine the position, nature and size of the image formed using the lens formula.

Why is sustainable management of natural resources necessary? Out of the two reuse and recycle which, in your opinion, is better to practice? Give reason.

Write the name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen is possible. State the essential condition for an addition reaction. Stating this condition, write a chemical equation giving the name of the reactant and the product of the reaction.

Given below are some elements of the modem periodic table. Atomic number of the element is given in the parentheses: A(4), B(9), C(14), 0(19), E(20)

(a) Select the element that has one electron in the outermost shell. Also write the electronic configuration of this element.

(b) Which two elements amongst these belong to the same group? Give reason/for your answer.

(c) Which two elements amongst these belong to the same period? Which one of the two has bigger atomic radius?

List four categories of contraceptive methods. State in brief two advantages of adopting such preventive methods.