## Respuesta :

**Answer:**

0.50 seconds

**Step-by-step explanation:**

The time it takes for an **echo** to **return** is the **time** it takes for the **sound** to make the **round trip** between the source and the reflecting object.

The boulder is 80 m away from the source, so the round-trip distance is 2×80 m = 160 m. At a speed of 320 m/s, it takes sound ...

(160 m)/(320 m/s) = 0.50 s

to make the round-trip.

**It will take 0.50 seconds to hear the echo**.

The **time **it will take to **hear **the **echo**, when the **speed **of a **sound **wave is 320 m/s is 0.50 **seconds.**

**What is the speed of sound?**

**Speed **of sound is the rate by which the **sound **wave travels. The speed of sound depends on the **medium **by which the sound wave is **travelling**.

The **speed **of the **wave **can be found out using the following **formula**.

[tex]s=\dfrac{d}{t}[/tex]

Here, (*d*) is the **distance **travelled by the **wave **and (t) is time taken by the **wave **to cover that **distance**.

A **boy **yells in a narrow **valley**. The **sound **reflects off of a boulder that is 80 m away.

For the **echo**, distance travelled will be **doubled **as it come back.Thus, the **distance **travelled by **sound **wave is,

[tex]d=2\times80\\d=160\rm\; m[/tex]

The **speed **of **sound **is 320 m/s. Put these **value **in the above formula as,

[tex]320=\dfrac{160}{t}\\t=0.5\rm\; s[/tex]

Thus, the **time **it will take to **hear **the **echo**, when the **speed **of a **sound **wave is 320 m/s is 0.50 **seconds.**

Learn more about the **speed of sound** here;

https://brainly.com/question/95976