# Physics Lesson 11.5.4 - Echo

[ 1 Votes ]

Welcome to our Physics lesson on Echo, this is the fourth lesson of our suite of physics lessons covering the topic of Sound Waves. Intensity and Sound Level, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.

## Echo

Echo is the phenomenon of sound reflection when it encounters a large obstacle. As a result, a listener can hear his voice twice: one when he produces the sound and the other when his voice turns back. This helps us calculate the distance from a cliff, a mountain, a building, etc. Let's consider an example.

### Example 1

A girl standing near a wall shouts and then she hears the echo of her voice after 3.2 s. Calculate the distance of the girl from the wall. Take the speed of sound in air equal to 343 m/s. ### Solution 1

The distance travelled by the sound is twice the distance of the girl from the wall as the sound turns back at the girl's ear after hitting the wall. Also, the speed of sound is constant because sound moves within the same medium (air) during the entire process. Thus, we apply the formula of uniform motion to calculate the distance s of the girl from the wall, i.e.

2s = v × t
= 343 m/s × 3.2 s
= 1097.6 m

Therefore, the distance s of the girl from the wall is

s = 1097.6 m/2
= 548.8 m

You have reached the end of Physics lesson 11.5.4 Echo. There are 7 lessons in this physics tutorial covering Sound Waves. Intensity and Sound Level, you can access all the lessons from this tutorial below.

## More Sound Waves. Intensity and Sound Level Lessons and Learning Resources

Waves Learning Material
Tutorial IDPhysics Tutorial TitleTutorialVideo
Tutorial
Revision
Notes
Revision
Questions
11.5Sound Waves. Intensity and Sound Level
Lesson IDPhysics Lesson TitleLessonVideo
Lesson
11.5.1Things You Already Know About Sound Waves
11.5.2Things You Need To Know About Sound Waves
11.5.3Limits of Audibility. Audible Sound. Infra and Ultrasound<
11.5.4Echo
11.5.5Intensity of Sound Waves
11.5.6Sound Level
11.5.7Loudness and Pitch

## Whats next?

Enjoy the "Echo" physics lesson? People who liked the "Sound Waves. Intensity and Sound Level lesson found the following resources useful:

1. Echo Feedback. Helps other - Leave a rating for this echo (see below)
2. Waves Physics tutorial: Sound Waves. Intensity and Sound Level. Read the Sound Waves. Intensity and Sound Level physics tutorial and build your physics knowledge of Waves
3. Waves Revision Notes: Sound Waves. Intensity and Sound Level. Print the notes so you can revise the key points covered in the physics tutorial for Sound Waves. Intensity and Sound Level
4. Waves Practice Questions: Sound Waves. Intensity and Sound Level. Test and improve your knowledge of Sound Waves. Intensity and Sound Level with example questins and answers
5. Check your calculations for Waves questions with our excellent Waves calculators which contain full equations and calculations clearly displayed line by line. See the Waves Calculators by iCalculator™ below.
6. Continuing learning waves - read our next physics tutorial: Electromagnetic Waves. Light

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