topic 4-5

Question 1

Standing waves

Answer 1

When a tensioned cord with both ends attached is plucked, the formed wave will travel to one end and come back inverted to the opposite end. Then you will have two waves traveling in opposite ways. Where the two waves meet, a destructive interference occur called node. Similarly, where the two waves are perpendicularly away, a constructive interference occur and it’s called antinode. Figure 4.4 shows the nodes and antinodes of a fixed string.

Question 2

resonance

Answer 2

When waves that vibrate at different frequencies meet, they will create a single vibration with a higher amplitude and a resonant frequency. The lowest resonant frequency is called natural frequency and corresponds to one antinode. If there is more than one antinode the resonant frequency will be higher.

Resonant frequencies are also called harmonics. The first harmonic corresponds to the natural frequency, the second harmonic is when there are two antinodes, the third harmonic when there are three antinodes and so on

Question 3

longitudinal and transversal waves

Answer 3

longitudinal: are paralel to wave displacement
transerversal: are perpendicular to wave diplacement

Question 4

sound

Answer 4

Sound is a longitudinal wave because the vibrating molecules move in the same direction of the wave.

Question 5

The speed of sound in different mediums.

Answer 5

in a metallic rod, sound in an gas, sound in an extended solid

Question 6

characteristics of sound

Answer 6

frequency depends on the mass of the string, its length and tension force.
intensity of sound is the energy at which sound propagates. Sound intensity is related to the power per unit area of the wave.

Question 7

doppler effect and the situations that may be present between an observer and a source.

Answer 7

the Doppler Effect refers to the apparent change in the frequency of a sound source when there is a relative movement of the source regarding to the listener. In other words, it’s the change in frequency that a person will hear if the person or the sound source moves.
when you hear an approaching ambulance at a high pitch and once it passes you, you hear a low pitch.