Match List I with List II

	List I (Current configuration)		List II (Magnitude of Magnetic Field at point O)
A.		I.	$${B_0} = {{{\mu _0}I} \over {4\pi r}}[\pi + 2]$$
B.		II.	$${B_0} = {{{\mu _0}} \over {4 }}{I \over r}$$
C.		III.	$${B_0} = {{{\mu _0}I} \over {2\pi r}}[\pi - 1]$$
D.		IV.	$${B_0} = {{{\mu _0}I} \over {4\pi r}}[\pi + 1]$$

Choose the correct answer from the options given below :

In Young's double slits experiment, the position of 5$$\mathrm{^{th}}$$ bright fringe from the central maximum is 5 cm. The distance between slits and screen is 1 m and wavelength of used monochromatic light is 600 nm. The separation between the slits is :

T is the time period of simple pendulum on the earth's surface. Its time period becomes $$x$$ T when taken to a height R (equal to earth's radius) above the earth's surface. Then, the value of $$x$$ will be :

Assume that the earth is a solid sphere of uniform density and a tunnel is dug along its diameter throughout the earth. It is found that when a particle is released in this tunnel, it executes a simple harmonic motion. The mass of the particle is 100 g. The time period of the motion of the particle will be (approximately)

(Take g = 10 m s$$^{-2}$$ , radius of earth = 6400 km)