Many discoveries in science have been accidental. This is true for plant hormones also. Can you justify this statement by giving an example? Also what term is used for such accidental findings?

Many secondary metabolites of plants have medicinal properties. It is their misuse that creates problem. Justify the statement with an example.

What is the term for the ability of a gene to have many effects? Give one example from human genetics.

Three married couples are to be seated in a row having six seats in a cinema hall. If spouses are to be seated next to each other, in how many ways can they be seated ? Find also the number of ways of their seating if all the ladies sit together.

Precise measurements of physical quantities are a need of science. For example, to ascertain the speed of an aircraft, one must have an accurate method to find its positions at closely separated instants of time. This was the actual motivation behind the discovery of radar in World War II. Think of different examples in modern science where precise measurements of length, time, mass etc. are needed. Also, wherever you can, give a quantitative idea of the precision needed.

The Class X students of a secondary school in Krishinagar have been allotted a rectangular plot of land for their gardening activity. Sapling of Gulmohar are planted on the boundary at a distance of lm from each other. There is a triangular grassy lawn in the plot as shown in the Fig. The students are to sow seeds of flowering plants on the remaining area of the plot.:- Taking A as origin find the coordinates of the vertices of triangle .What will be the coordinates of the vertices of triangle PQR if C is the origin ? Also calculate the areas of the triangles in these cases. What do you observe ?

Freons, chlorofluoro compounds of methane and ethane are stable, low boiling, non-toxic, non-inflammable and non-reactive compounds. These are extensively used in refrigerators and air conditioners. These are also used as propellants for aerosols and foams to spray out deodorants, cleansers, shaving creams and hair sprays. However, its use has been discouraged and restricted in some countries. As a student of science, What is freon-12? How is it prepared?

Freons, chlorofluoro compounds of methane and ethane are stable, low boiling, non-toxic, non-inflammable and non-reactive compounds. These are extensively used in refrigerators and air conditioners. These are also used as propellants for aerosols and foams to spray out deodorants, cleansers, shaving creams and hair sprays. However, its use has been discouraged and restricted in some countries. As a student of science, What values are associated with this decision ?

You have heard about serveral insectivorous plants that feed on insects. Nepenthes or the pitches plant is one such example. Which usually grows in shallow water or in marsh lands. What part of the plant os modified into a 'pitcher'? How does this modification help the plant for food even though it can photosynthesize like any other green plant?

classically an electron can be in any orbit around nucleus of an atom. Then what determines the typical atomic size? Why is an atom not, say, thousand times bigger than its typical size? Thequestion had greatly puzzled Bohr before he arrived at his famous model of the atom that you have learnt in the text. To simulate what he might well have done before his discovery, let us play as followswith the basic constants of nature e, me, c and see if we can get a quantity with the dimensions of length that is roughly equal to the known size of an atom (~ 10 m).- You will find that the length obtained above is many orders of magnitude smaller than the atomic dimensions. Further, it involves c. But energies of atoms are mostly in non-relativistic domain where c is not expected to play any role. This is what may have suggested Bohr to discard c and look for else h had already made its appearance elsewhere. Bohr lay in recognising that h, m_e , and e will yield the right atomic size. Construct a quantity with the dimension of length from h, me, and e and confirm that its numerical value has indeed the correct order of magnitude.

Classically, an electron can be in any orbit around the nucleus of an atom. Then what determines the typical atomic size? Why is an atom not, say, thousand times bigger than its typical size? The question had greatly puzzled Bohr before he arrived at his famous model of the atom that you have learnt in the text. To simulate what he might well have done before his discovery, let us play as follows with the basic constants of and see if we can get a quantity with the dimensions of length that is roughly equal to the known of an atom (~ 10^ -10 m).- Construct a quantity with the dimensions of length from the fundamental constants e, m_e , and c. Determine its numerical value.