6. Pick up the correct specification of Ramsden eyepiece from the following :
Options
A. it consists of two equal piano convex lenses
B. the curved surfaces of plano-convex lenses face each other
C. the two lenses are separated by a distance equal to 2/3 of the focal length of either lens.
D. the distance between the diaphragm and the front lens of the eyepiece is kept equal to 1/4 th of the focal length of a lens so that rays from a point on the diaphragm enter the eye as a parallel beam
8. A dumpy level is set up with its eye-piece vertically over a peg A. The height from the top of peg A to the centre of the eye-piece is 1.540 m and the reading on peg B is 0.705 m. The level is then setup over B. The height of the eye-piece above peg B is 1.490 m and a reading on A is 2.195 m. The difference in level between A and B is