question_answer

Let \[u=\hat{i}+\hat{j},\,v=\hat{i}-\hat{j}\] and \[w=\hat{i}+2\,\hat{j}+3\,\,\hat{k}\]. If \[\hat{n}\] is a unit vector such that \[u\,.\,\,\hat{n}=0\] and \[v\,.\,\,\hat{n}=0\], then \[\left| w\,.\,\,\hat{n} \right|\] is equal to     AIEEE  Solved  Paper-2003

A) 0                             

B) 1                             

C) 2                             

D) 3

Correct Answer: D

Solution :

Since,  and                               Now, and