Answer:
d' = 75.1 cm
Explanation:
It is given that,
The actual depth of a shallow pool is, d = 1 m
We need to find the apparent depth of the water in the pool. Let it is equal to d'.
We know that the refractive index is also defined as the ratio of real depth to the apparent depth. Let the refractive index of water is 1.33. So,

or
d' = 75.1 cm
So, the apparent depth is 75.1 cm.
You said that she's losing 1.9 m/s of her speed every second.
So it'll take
(6 m/s) / (1.9 m/s²) = 3.158 seconds (rounded)
to lose all of her initial speed, and stop.
The frequency of a sound wave is the number of cycles of a sound wave per second or Hertz (Hz). The frequency can be calculated by dividing wavelength by time (Figure 1.3). A small wavelength will yield a higher frequency, whereas a larger wavelength will yield a smaller frequency.