Courses
Courses for Kids
Free study material
Offline Centres
More
Store

# Define frequency and wavelength with reference to sound. Explain what is echo. Write full form of SONAR. Give any one application of ultrasound.

Last updated date: 13th Jun 2024
Total views: 403.8k
Views today: 6.03k
Verified
403.8k+ views
Hint:-A sound is a vibration in an elastic medium at a frequency , wavelength and intensity that is capable of being heard by the human ear. Sound is propagated through an elastic fluid as a longitudinal sound wave.

Complete step-by-step solution:Frequency :-
The number of vibrations that a sound wave is making is called its frequency ( f ).
Frequency can also be defined as the number of waves passing a given point in one second.
Frequency is measured in hertz (Hz).
Wavelength :- It is the distance travelled by a wave during one complete vibration.
Wavelength represents the distance between two nearest crests or troughs.
In simple words wavelength is the length of one wave.
Wavelength is denoted by lambda ($\lambda$).
The S.I unit of wavelength is metre (m).
Echo :- Echo is based on the reflection of sound . An echo is defined as repetition of sound due to reflection.
1. There are a number of tourist places where echo points are marked and at those places if you shout something you will hear back your sound after sometimes. This phenomenon is Echo .
2. There are certain conditions required for an echo to be heard , these conditions are
3. The minimum distance between the source of sound and refracting body should be 17 metres.
4. The wavelength of the sound should be less than the height of the reflecting body.
5. The intensity of the sound should be sufficient so that it can be heard after reflection.
SONAR – The word ‘ SONAR ‘ stands for “ Sound Navigation and Ranging “
Application of ultrasound
Welding metal : ultrasound is used for welding metals like tungsten which can-not be welded by conventional methods. In this welding one of two pieces of the tungsten is held firmly against the other piece and then vibrated with an ultrasonic vibrator. The heat produced due to friction at the point of contact melts the metal. When we stop the vibrator the metal ends of metal fuse to form a tight weld.

Note:- There are various other places where ultrasound is used these are
Medical use – Ultrasound scanning of human body / pet body .
Ultrasound detection of defects in metals :- Metallic components are used in buildings , bridges, machines , scientific equipment and so on ,if there are cracks or holes inside the metal used the strength of the structure or component is reduced and it can fail . Such defects are not visible from the outside but ultrasonic waves are used to identify such defects.
Drilling holes or making cuts of desired shapes, Ultrasound cleaning etc.