Arms cache found near Afghan border

The video tutorial introduces the concept of echo, explaining its basic principles and how it occurs in acoustics.

What is an echo?

• A sound that is absorbed by surfaces

• A sound that is created by a musical instrument

• A sound that is reflected back to the listener

• A sound that is amplified by a microphone

Which condition is necessary for an echo to occur?

• The surface must be hard and reflective

• The surface must be soft and absorbent

• The sound must be high-pitched

• The sound must be loud and continuous

How does the distance between the source and the reflecting surface affect an echo?

• It has no effect on the echo

• A shorter distance results in a clearer echo

• A greater distance results in a louder echo

• A greater distance results in a delayed echo

In which field is the use of echoes particularly significant?

• Painting

• Gardening

• Medicine

• Cooking

What is one application of echoes in technology?

• Echoes are used in digital photography

• Echoes are used in sonar systems

• Echoes help in noise cancellation

• Echoes are used in solar panels