Physics Chapter 12

Why does a struck tuning fork sound louder when its handle is held against a table?

A tuning fork sound louder because the table is forced to vibrate and its larger surface sets more air in motion.

What does it mean to say that one wave is out of phase with another?

A wave is said to be out of phase with another if the crest of one falls at the trough of another and trough of one falls at the crest of another.

What kinds of waves exhibit interference?

All kind of waves (e.g., sound, light, water, etc.) exhibit interference.

How does a vibrating tuning fork emit sound?

Any vibrational object produces sound. We can produce sound waves in a tuning fork by setting a vibration up in a medium, such as air. In such a case, the atoms in the medium vibrate and hence produce sound waves.

What is a wiggle in time called? A wiggle in space and time?

Anything that can move to and fro or back and forth is called vibration. A wiggle in time is called vibration. A wiggle in space and time is called wave. A wave is disturbance over the space.

Distinguish between constructive interference and destructive interference.

Constructive interference between two waves occurs when they travel in phase. In this case crest of one wave overlaps the crest of another wave and also the trough of one wave overlaps the trough of another wave. In this situation, the amplitude of the resultant wave increases. Destructive interference between two waves occurs when they travel out of phase. In this case crest of one wave overlaps the trough of another wave, in this situation, the amplitude of the resultant wave decreases.

Can the Doppler effect be observed with longitudinal waves, with transverse waves or both?

Doppler effects can be observed for both type of waves. Doppler effect in sound (longitudinal waves) and light (transverse waves) is well Known.

In one word , what is it that moves from source to receiver in wave motion?

Energy.

What is required to make an object resonate?

Every elastic body have its own natural frequency. If we can apply force to the object to vibrate such that the applied forced frequency is equal to natural frequency of the object, the object vibrates with resonant frequency. In this situation it can produce maximum amplitude. Thus, to produce resonance in an object, we stimulate the object to its natural frequency.

True or false: A sonic boom occurs only when an aircraft is breaking through the sound barrier. Defend your answer

False

True or false: In order for an object to produce a sonic boom, it must be " noisy" give to examples to support your answer

False. Sonic boom occurs only when an object breaks the sound barrier. When an aircraft is travels at or in excess of sound barrier, sonic boom occurs.

Distinguish between forced vibrations and resonance.

Forced vibrations are the vibrations caused by a vibrating force. For example, the vibrations developed in the factory flow due to the heavy machinery are forced vibrations. Resonance occurs when the frequency of external source and the natural frequency of the object matches. This results in a dramatic increase in the amplitude.

How do frequency and period relate to each other?

Frequency and period of a wave are related by the following relation. Frequency (V) = 1/period (t)

How does the V shape of a bow wave depend on the speed of the wave source?

Higher the speed of the wave source, narrower the v-shape of the bow wave.

In the Doppler effect, does frequency change? Does wavelength change? Does wave speed change?

In the Doppler Effect, frequency and wavelength change but wave speed remains unchanged.

In what direction are the vibrations in a transverse wave, relative to the direction of wave travel?

In transverse waves, the direction of particle displacement is perpendicular to the direction wave travel. Example: propagation of light waves.

What physical phenomenon underlies beats?

Interference!

What is the law of reflection for sound?

Law of reflection for sound - The law of reflection of sound states that the angle of incidence is equal to the angle of reflection.

There is a difference between the way in which we passively see our surroundings in daylight and the way in which we actively probe our surroundings with a searchlight in the darkness. Which of these ways of perceiving our surroundings is more like the way in which a dolphin perceives its environment?

More like in the nighttime with a searchlight as they locate and identify everything with sound.

Distinguish between a musical sound and noise.

Musical Sound: Musical sound corresponds to the sound waves which repeat their shape periodically. These are produced by a regularly vibrating source. These sources produces regularization of the eardrum. Noise: noise corresponds to the sound waves which do not repeat their shape periodically. These are produced by an irregularly vibrating source. These sources produce irregular vibrations of the eardrum.

Does a blob of putty have a natural frequency? Explain

No the blob of putty doesn't have natural frequency. In order to get vibrations, the substance must have elastic nature. But the blob of putty is malleable. It is not elastic. Thus, its doesn't have natural frequency.

Does the medium in which a wave travels move with the wave? Give examples to support your answer.

No, the medium does not travel with the wave. For example, when we speak, the air layer close to our lip remains close to the lip even when sound wave reaches the eardrum of the receiver. Similarly when water wave is produces by throwing a stone in a pond end a leaf placed at some point, the leaf vibrates up and down but it does not travel with the water wave.

What is a node? What is an antinode?

Nodes are the points on a standing wave pattern where displacement is zero. These points act as if they are clipped. Antinodes are the points on a standing wave pattern where displacement is maximum antinodes occur halfway between nodes.

Distinguish between these different parts of a wave: period, amplitude, wavelength and frequency.

Period: Period of a wave is the time required for a vibration of a wave to make a complete cycle. For example, if a pendulum makes ten vibrations in one second, its period will be 1/10 second. Amplitude: Amplitude of a wave is the maximum displacement from equilibrium position. In a transverse wave amplitude refers to the distance from the midpoint to the crest ( also from the midpoint to the trough) of the wave. Wavelength: Wavelength of a wave is the distance between successive crests, troughs or identical parts of a wave. Frequency: Frequency of a wave refers to the total number of vibrations completed in unit time. For example, if a pendulum makes ten vibrations in one second the frequency of pendulum is ten hertz (cycles per second)

What causes refraction?

Refraction occurs as light passes through boundary of two media. In the case of a wave travel from one medium to another medium; the speed of the wave is changes at the interface of two media. Thus, the wave refracts at the interface of two media.

What is a reverberation?

Reverberation is reechoed sound caused due to multiple reflections of sound waves.

Does sound travel faster in warm air or in cold air? Defend your answer?

Sound travel faster in warm air as faster moving molecules at higher temperature pump into each other more frequently. Thus a pulse is transmitted in less time in a warm air.

Distinguish between the propagation of sound waves and the propagation of light waves.

Sound waves are mechanical waves. In order to propagate sound waves, a medium is necessary; whereas light waves are electromagnetic waves which didn't require any medium to propagate. Light wave can travel in vacuum also.

Distinguish between a compression and a rarefaction.

The compression and rarefactions are produced in longitudinal wave. The compression are the region of high pressure. In compression, atoms are squeezing together. The rarefaction are region of low pressure. In a rarefaction atoms are stretching out.

In what direction are the vibrations in a longitudinal wave, relative to the direction of wave travel?

The direction of particle displacement is in the same direction as wave travel.

How many vibrations per second are represented in a radio wave of 101.7 MHz?

The number of vibrations per second is called frequency. The units for frequency are HZ. The given frequency is 101.7 MHz. It is equal to the number of vibrations per second here, one Hz represents "one vibration per second". 101.7 MHz = (101.7 MHz) (10^6 hz/1 MHz)= 101700000 therefore the number of vibrations per second is 101700000

How does the speed of sound in water compare with the speed of sound in air? How does the speed of sound in steel compare with the speed of sound in air?

The speed of sound in water is four times of the speed of sound in air. The speed of sound in steel if fifteen times of the speed of sound in air.

Why do troops "break Step" when crossing a bridge?

Troops break step when crossing a bridge as bridge may collapse if the natural frequency of the bridge matches with the frequency of the steps of troops. To avoid resonance, troops break their steps on a bridge.

What is the source of all waves?

Vibration is a wiggle in time. A wiggle in space and time is wave. All vibrating bodies produce waves. So vibration is the source of all waves.

What is the relationship among frequency, wavelength, and wave speed?

Wave speed (v) = Frequency (V) x Wavelength

How do the speed of a wave source and the speed of the waves themselves compare when a wave barrier is being produced? How do they compare when a bow wave is being produced?

When a wave barrier is being produced, the speed of the wave source and the speed of the waves will be equal. When a bow wave is produced, the speed of the wave-source and the speed of the waves will be different, speed of the wave source being more compared to the wave speed.

When you listen to a radio, why do you hear only one station at a time instead of all stations at once?

When you tune a radio, you are similarly adjusting the natural frequency of the tuned circuit in the device to match one of the many surrounding signals. Then the device resonates to one station at a time of playing instead all station at once.

What cases a standing wave?

Whenever two waves of the same frequency and amplitude superimpose with one another while traveling opposite directions along the same medium, standing waves are formed.

Why are there typically more stringed instruments in an orchestra than wind instruments?

Yes, generally there are more string instruments in an orchestra. Because, the efficiency of stringed instruments have basically less compare to wind instruments in transmitting the vibrations to a sound chamber.

Does sound tend to bend upward or downward when its speed near the ground is lower than its speed higher up?

Yes, the sound bends towards downward when its speed near the ground is lower than its speed higher up. Because sound can also exhibit refraction.