Magnetism and Matter - Result Question 11

15. If θ1 and θ2 be the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dipθ is given by :-

(a) tan2θ=tan2θ1+tan2θ2

[2017]

(b) cot2θ=cot2θ1cot2θ2

(c) tan2θ=tan2θ1tan2θ2

(d) cot2θ=cot2θ1+cot2θ22

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Answer:

Correct Answer: 15. (d)

Solution:

  1. (d) If θ1 and θ2 are opparent angles of dip Let α be the angle which one of the plane make with the magnetic meridian.

tanθ1=vHcosα

i.e., cosα=vHtanθ1

tanθ2=vHsinα,

i.e., sinα=vHtanθ2

Squaring and adding (i) and (ii), we get

cos2α+sin2α=(VH)2(1tan2θ1+1tan2θ2) i.e., 1=V2H2[cot2θ1+cot2θ2]

or H2V2=cot2θ1+cot2θ2

i.e., cot2θ=cot2θ1+cot2θ2



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