JEE Advanced 2023 · Introduction to Three Dimensional Geometry
Let ℓ1 and ℓ2 be the lines r1=λ(i^+j^+k^) and r2=(j^−k^)+μ(i^+k^), respectively.
Let X be the set of all the planes H that contain the line ℓ1.
For a plane H, let d(H) denote the smallest possible distance between the points of ℓ2 and H.
Let H0 be a plane in X for which d(H0) is the maximum value of d(H) as H varies over all planes in X.
Match each entry in List-I to the correct entries in List-II.
| List-I | List-II |
| --- | --- |
| (P) The value of d(H0) is | (1) 3 |
| (Q) The distance of the point (0,1,2) from H0 is | (2) 31 |
| (R) The distance of origin from H0 is | (3) 0 |
| (S) The distance of origin from the point of intersection of planes y=z, x=1 and H0 is | (4) 2 |
| | (5) 21 |
The correct option is:
Let ell₁ and ell₂ be the lines r⃗₁ = λ(î+ĵ+k̂) and r⃗₂ = (ĵ-k̂) + μ(î+k̂), respectively. Let X be the set of all the planes H that contain the line ell₁. For a plane H, let d(H) denote the smallest possible distance between the points of ell₂ and H. Let H₀ be a plane in X for which d(H₀) is the maximum value of d(H) as H varies over all planes in X. Match each entry in List-I to the correct entries in List-II. | List-I | List-II | | --
ℓ1:r=λ(i^+j^+k^)⇒through (0,0,0),d1=(1,1,1)ℓ2:r=(j^−k^)+μ(i^+k^)⇒through (0,1,−1),d2=(1,0,1)X={H:ℓ1⊂H},d(H)=mindist(ℓ2,H)H0∈X maximises d(H)Match (P),(Q),(R),(S) with (1)–(5)1.H:n⋅r=0,n⊥d12.d(H)=0 unless ℓ2∥H3.maximise d(H)⇒H0, then (P),(Q),(R),(S)H:n⋅r=0(through O)n⊥d1⇒n1+n2+n3=0d2⋅n=n1+n3d2⋅n=0⇒ℓ2 meets H⇒d(H)=0d(H)=0⇒n1+n3=0n2=0,n∥(1,0,−1)H0:x−z=0d(H0)=∣n∣∣n⋅OA∣,A(0,1,−1),n=(1,0,−1)n⋅OA=1,∣n∣=2d(H0)=21⇒(P)→(5)dist((0,1,2),H0)=2∣0−2∣=22=2⇒(Q)→(4)O(0,0,0)∈H0⇒dist(O,H0)=0⇒(R)→(3)y=z,x=1,x=z⇒(1,1,1)dist from O=1+1+1=3⇒(S)→(1)(P)→(5),(Q)→(4),(R)→(3),(S)→(1)Answer: Option (2)
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