**Question:**

An observer on Earth observes a star performing simple harmonic motion as it moves periodically from point A to point B then back to point A. She determines that it takes 18 days for the star to move from A to B. What is the frequency of the star’s oscillation? Give your answer in uHz, correct to two significant figures and without units.

**Answer:**

Frequency = 1 / time period

Now time period for one complete oscillation = time ro go from A to B + time to go from B to A

= 18 days + 18 days = 36 days = 36 × 24 × 60 × 60 seconds = 3110400 seconds.

Hence, frequency = 1/ (3110400 s) = 0.32 × 10^{-6} Hz

In micro Hertz, frequency = **0.32** ( Answer)