B.Ed. Physics teaching method Pedagogy of physics Sound sound waves Doppler effect

1. B.Ed. Course 205 = 15 PHYSICS
Pedagogy of School Subject
Dr. Namita S. Sahare
Tilak College of Education , Pune
India

2. WAVE INTERACTIONS
205 – 15 : Physics
Understanding disciplines and
Pedagogy of school subject

3. Introduction
• Sound originates from vibrating or oscillating
objects, such as vocal cord in the human
throat , the skin of the drum .
• The vibrations are then passed through a
medium, they strike the ear drum, the ear
converts the vibrations into nerve impulses,
which pass to brain where they are
interpreted as sounds.

4. Some Definitions
• Periodic Motion
• Oscillatory or Vibrating Motion
• Oscillation
• Period of Oscillation(T)
• Frequency(n)
• Amplitude

5. Types of Waves
• Mechanical Waves: Waves which require material
medium for their propagation are mechanical
waves.
Ex.: Waves over a stretched string, waves on the
water surface, sound waves, etc
• Electromagnetic Waves: One of the waves that
are propagated by simultaneous periodic
variations of electric and magnetic field intensity.
Ex.: Light Waves, Radio Waves, Xrays, etc

6. Sensors

7. Longitudinal Wave
wave particles vibrate back
and forth along the path that
the wave travels.
Compressional Wave

8. • Compressions
The close together part of the wave
• Rarefactions
The spread-out parts of a wave

9. Longitudinal Wave
• A wave in which particles of medium vibrate in
a direction parallel to the direction of
propagation of the direction parallel to the
direction of propagation of the wave is called
Longitudinal wave.

10. Sound As A Longitudinal Wave
Motion
• Sound wave are longitudinal wave which can
travel through gas, liquid or solid medium. The
propagation of sound wave in air can be easily
understood by considering the vibrations of
tuning fork.

11. Transverse waves
wave particles vibrate
in an up-and-down motion.

12. Transverse waves
• Crests
Highest part of a wave
• Troughs
The low points of the wave

13. Amplitude-
is the maximum distance
the particles in a wave
vibrate from their rest positions.
Frequency
- the number of waves
produced in a given time

14. Waves transfer energy without
transferring matter.
Frequency= waves/time

15. Wave Velocity - is the speed with which a wave
crest passes by a particular point in space
It is measured in meters/second.
Wave Velocity = Frequency  Wavelength

16. Speed of Sound
• Medium velocity m/sec
air (20 C) 343
air (0 C) 331
water (25 C) 1493
sea water 1533
diamond 12000
iron 5130
copper 3560
glass 5640

17. II. Properties of Sound
Pitch
- description of how high or low
the sound seems to a person
Loudness-
how loud or soft a sound is
perceived to be.

18. Ultrasound
- sound waves with frequencies above the
normal human range of hearing.
Sounds in the range from 20-100kHz
Infrasound
- sounds with frequencies below the
normal human range of hearing.
Sounds in the 20-200 Hz range

20. Interference
• the result of two or more sound
• waves overlapping

21. Different sounds that you hear include
(A) noise, (B) pure tones, and (C) musical notes.

23. Standing sine wave patterns of air vibrating in a closed
tube. Note the node at the closed end and the antinode
at the open end. Only odd multiples of the fundamental
are therefore possible.

24. Standing waves in these open tubes have an antinode at
the open end, where air is free to vibrate.

25. Relation Between Velocity, Wavelength & frequency
• Period (T): The time required to complete one vibration by
a particle of medium is called period (T) of wave. Each
particle of medium vibrates with same period. It’s SI unit is
second(s).
• Frequency (n): The number of vibrations performed by any
particle of medium per second is called frequency (n) of
wave. The frequency is related to period as n=1/T. SI unit of
frequency is called hertz (Hz).
• Wavelength : The distance between two successive
particles, which are in same state of motion or in same
phase is called wavelength ( ) of wave.

26. Wavelength
• Wavelength ( ): The distance between two
successive particles, which are in same state
of motion or in same phase is called
wavelength ( ) of wave.

27. Relation Between Velocity, Wavelength
and frequency
• Velocity (v): The distance covered by the disturbance or a
wave per second is called velocity of the wave.
In one period (T), the wave covers the distance equal to
wavelength( ). Therefore velocity of wave is given by
Magnitude of velocity =
v =
but n = v = n
Wave Velocity = Frequency  Wavelength

28. Doppler Effect
is the apparent change in the
frequency of a sound caused by
the motion of either the listener
or the source of the sound.

30. • Sounds from Moving Sources.
– A moving source of sound or a moving observer
experiences an apparent shift of frequency
called the Doppler Effect.
– If the source is moving as fast or faster than the
speed of sound, the sound waves pile up into a
shock wave called a sonic boom.
– A sonic boom sounds very much like the
pressure wave from an explosion