The frequency of plane progressive wave is 100 Hz. After how much time the same point will be `90^@` out of phase ?

Explanation

To solve the problem of determining the time it takes for a point on a plane progressive wave to be 90 degrees out of phase, we can follow these steps:

### Step 1: Understand the relationship between phase, frequency, and time
The phase difference (θ) in a wave can be expressed as:
\[ \theta = \omega t \]
where:
...