3RD TERM

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APPLICATION OF SOUND WAVES

(A) WIND INSTRUMENTS
Clarinets, flute, saxophone, trumpet are examples of wind musical instruments. A musical note originates from a source vibrating in a uniform manner with on or more constant frequencies music is a combination of musical notes. All wind instrument use resonating
air columns to produce their sounds. Sounds from wind instruments may originate from (1) Air vibrating over an opening e.g. organ and flute.
(2) The vibrating lips of a brass instrument e.g. trumpet.
(3) A vibrating heel e.g. clarinet, saxophone.
Some columns are of fixed length, their resonant frequencies being altered by the opening or the closing of holes in the column e.g. clarinet, a recorder, some instruments are played by altering the length the air column e.g. a trumpet.
https://youtu.be/bk_qfil8bYU

(B)STRINGED INSTRUMENTS
The guitar, the sonometer and piano are examples of stringed musical instruments. These instruments may be set in vibration by a bow, or plucked with a finger e.g. a violin is bowed while a guitar is plucked. The frequency of a vibrating string depends on its length, the mass and the force that keeps the string taut. Stringed instruments vibrate as a whole and in loops at the same time e.g. the violin. These vibrations produce both the fundamental and overtones frequencies.
https://youtu.be/q98A5ev9MYY

(C) PERCUSSION INSTRUMENTS (drums, bell, talking drum)
Percussion instruments produce musical notes when they are struck or hit. They have rods, plates or membranes that vibrate when struck; for example, there are rods in bells, plates (bars) in xylophones and membrane in drums.
https://youtu.be/6QA5KnKpKbk

ECHOES AND THEIR APPLICATION
An echo is the repetition of sounds caused by the reflection of sound waves from a hard surface. Such as buildings, walls and cliffs are good reflector of sound.
Echoes have practical importance in the development of sonar, speed traps, prospecting for oil and determining the speed of sound. In the determination of speed of sound by echo, we use the expression

2x = V t

Where
V = velocity of sound x = distance between the source of sound and reflecting surface
t = total time taken

https://youtu.be/GuvYffYISJc

https://youtu.be/argVRiFZtWk

General revision
An electric heater immersed in some water raises the temperature of the water from 40ºC to 100ºC in 6min. After another 25min, it is noticed that half the water has boiled away. Ignoring heat lost to the surrounding, calculate the specific latent heat of vaporisation of water


ASSIGNMENT
1 The natural frequency of a simple pendulum depends only on
A area B amplitude C length D speed
2 A tuning fork sounds louder when its stem is pressed against a table top than when held in air because
(a) a larger mass of air is set vibrating by the table top (b) the whole table vibrates in resonance
( c) the whole table has acquire a larger frequency (d) the fork and the table have the same frequency
3 What type of motion does the skin of a talking drum perform when it is being struck with drumstick (A) random (B) rotational (C) vibratory (D) translational
4 which of the following statement is not true
(A) musical notes consists of combination of sounds of regular frequency
(B) sound travels faster in solids than in gases
(c ) the loudness of sound is determine by its frequency
(D) the pitch of a note depend on the frequency of vibration of the source
5 Calculate the wavelength of a note which is one octave lower than a note of 256 Hz in a medium in which the speed of sound is 352m/s (A) 0.69m (B) 1.38m (C ) 2.75m ( D ) 5.50m
THEORY
1 What do you understand by the term resonance?
2 An object 5cm high is placed at a distance of 12cm from a convex lens of focal length 8cm, calculate the position and nature of the image produced.

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REVISION