Two concave lenses of 60 cm focal length are cemented on either side of a convex

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Question
Two concave lenses of 60 cm focal length are cemented on either side of a convex lens of 15 cm focal length. The focal length of the combination is
Options
A. 10 cm
B. 20 cm
C. 30 cm
D. 40 cm

Correct Answer

30 cm

Surveying problems

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2. If S is the length of a subchord and R is the radius of simple curve, the angle of deflection between its tangent and sub-chord, in minutes, is equal to
Options
A. 573 S/R
B. 573 R/S
C. 171.9 S/R
D. 1718.9 R/S
E. 1718.9 S/R.

3. Pick up the correct statement from the following :
Options
A. the eyepiece plays no part in defining the line of sight
B. the diaphragm plays no part in defining the line of sight
C. the optical centre of the objective plays no part in defining the line of sight
D. none of these.

6. Pick up the method of surveying in which field observations and plotting proceed simultaneously from the following
Options
A. chain surveying
B. compass surveying
C. plan table surveying
D. tacheometric surveying.

7. The most reliable method of plotting a theodolite traverse, is
Options
A. by consecutive co-ordinates of each station
B. by independent co-ordinates of each station
C. by plotting included angles and scaling off each traverse leg
D. by the tangent method of plotting.

8. If h is the difference in level between end points separated by l, then the slope correction is . The second term may be neglected if the value of h in a 20 m distance is less than
Options
A. m
B. 1 m
C. 2 m
D. 3 m

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