If `veca, vecb,vecc` are unit vectors such that `veca.vecb = 0= veca.vecc` and the angle between `vecb and vecc is pi//3` then the value of `|vecaxxvecb -veca xx vecc|` is

Options

A. `1//2`
B. 1
C. 2
D. none of these

Answer

b

Explanation

`|vecaxxvecb-vecaxxvecc|^(2)=|vecaxx(vecb-vecc)|^(2)`
`|veca|^(2)|vecb-vecc|^(2)`
`-(veca.(vecb-vecc))^(2)=|vecb-vecc|^(2)`
`= |vecb|^(2)+|vecc|^92)-2|vecb||vecc|cos (pi/3)=1`