# Echo Location

We have seen previously that when light is incident on a surface, reflection can occur. This is also true for all other types of wave. Here, we will look at several types of reflected waves and their uses.

## Sound and Echo-Location

We are all aware that when sound hits a solid object ( such as a cave wall ) the sound will be reflected back to us in the form of an Echo.

By timing how long this echo takes to arrive, we can estimate the distance to the cave wall. This process is called Echo-Location.

## How to calculate Range

In order to use Echo-Location, we must first know:-

• The speed of sound in that medium

• The time taken for the sound wave to reach the object and return

Then we can simply use the following formula:-

Note - The path the transmitted sound wave takes is to the object and back again. This means any distance found through this method must be halved in order to find the Range ( distance to

object ).

The videos below show the concept of Echo-Location in the film The Dark Knight.

The technology shown in this film is not real, but the basic concept of generating a "map" of the surrounding area using Echo-location is possible.

SONAR

SONAR ( Sound Navigation and Ranging ) used by ships uses a form of echo-location to build up an image of the surrounding area, to detect other vessels or locate fish.

In the natural world we find several animals that do not rely on eyesight to hunt prey or to navigate, but use echo-location instead.

The video below shows how Bats use Echo-Location to find Prey.