Complex Numbers And Quadratic Equations question 633

Question: If $ \omega =\frac{z}{z-\frac{1}{3}i} $ and $ |\omega |=1, $ then z lies on

Options:

A) an ellipse

B) a circle

C) a straight line

D) a parabola

Show Answer

Answer:

Correct Answer: C

Solution:

As given $ \omega =\frac{z}{z-\frac{1}{3}i}\Rightarrow |\omega |=\frac{|z|}{|z-\frac{1}{3}i|}=1 $
$ \Rightarrow |z|=| z-\frac{1}{3}i | $
$ \Rightarrow $ distance of z from origin and point $ ( 0,\frac{1}{3} ) $ is same hence z lies on bisector of the line joining points $ (0,0) $ and $ (0,1/3) $ . Hence, z lies on a straight line.