D.D.T. is one of the most powerful insecticide which is effective against the mosquitoes that spread malaria. Mukesh’s mother wanted to buy D.D.T. from the market to use at night to protect her family from mosquitoes. But Mukesh stopped his mother from purchasing D.D.T. What values are attached to suggestion of Mukesh ?

(a) What is galvanisation ? (b) Give three methods to protect iron from rusting. (c) Discuss the factors responsible for rusting of iron or corrosion. (d) Name a chemical which is used for preventing rusting of iron.

A magnet is suspended vertically from a fixed point by means of a spring, as shown in the figure. One end of the magnet hangs inside a coil of wire. The coil is connected in series with a resistance R. The magnet is displaced vertically a small distance D and the released. shown in the figure variation with time t of the vertical displacement d of the magnet from its equilibrium position. State and explain, by reference to electromagnetic induction, the nature of the oscillations of the magnet. Calculate the angular frequency omega_0 of the oscillations.

A point source S emitting light of wavelength 600 nm is placed at a very small height h above a flat reflecting surface AB [Fig.6.07].The intensity of the reflected light is 36% of the incident intensity.Interfrerence fringes are observed on a screen placed parallel to the reflecting surface at a very large distance D from it. If the intensity t pint P corresponds to a maximum,calculate the minimum distance through which the reflecting surface AB sould be shifted so that the intensity at P again becomes maximum.

A proton is kept at rest. A positively charged particle is released from rest at a distance d in its field. Consider two experiments, one in which the charged particdle is also a proton and in another, a positron. In the same time t, the work done on the two moving charged particles is

Two medians drawn from the acute angles of a right angled triangle intersect at an angle pi/6dot If the length of the hypotenuse of the triangle is 3u n i t s , then the area of the triangle (in sq. units) is sqrt(3) (b) 3 (c) sqrt(2) (d) 9

The question given below consist of an assertion (A) and a reason ( R). Use the following key to choose the appropriate answer to these questions from the codes (a), (b), ( c) and (d) given below: (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is NOT the correct explanation of A. (c) A is true but R is false. (d) A is false and R is also false. Assertion: A convex lens of focal length 30 cm and can't be used as a simple microscope in normal setting. Reason: For normal setting, angular magnification of simple microscope is M=D//F .

consider the statements given below regarding contraception answer as directed thereafter. (a) medical termination of pregnancy (MTP) during first trimester is generally save, (b) generally chances of conception are Nil until mother breast-feeds the infant up to 2 years. (c) intrauterine devices like copper-T are effective contraceptives. (d) Contraceptive pills may be taken up to 1 week after coitus to prevent conception. which two of the above statements are correct?

Let P_i and P_i ' be the feet of the perpendiculars drawn from the foci Sa n dS ' on a tangent T_i to an ellipse whose length of semi-major axis is 20. If sum_(i=0)^(10)(S P_i)(S^(prime)Pi ')=2560 , then the value of eccentricity is (a) 1/5 (b) 2/5 (c) 3/5 (d) 4/5

f and h are function from A rarr B, where A = {a, b, c, d} and B = {s, t, u} defined as follows f(a) = t, f (b) = s, f(c ) = s f(d) = u, h(a) = s, h(b) = t h(c ) = s, h(a) = u, h(d) = u Which one of the following statement is true?

A source contains two phosphorous radio nuclides "_15^32P (T_(1/2) = 14.3d) and "_15^33P (T_(1/2) = 25.3d) . Initially, 10% of the decays come from "_15^33P . How long one must wait until 90% do so?