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What Is Amplitude In Physics

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The Relationship Between Wave Frequency Period Wavelength And Velocity

What is Amplitude? | Waves | Physics


just as in the case of harmonic motion of an object. We can see from this relationship that a higher frequency means a shorter period. Recall that the unit for frequency is hertz , and that 1 Hz is one cycleâor one waveâper second.

The speed of propagation vw is the distance the wave travels in a given time, which is one wavelength in a time of one period. In equation form, it is written as

From this relationship, we see that in a medium where vw is constant, the higher the frequency, the smaller the wavelength. See Figure 13.8.

Amplitude Of Material Waves Determines Energy

For waves that require a material medium, like water waves or sound waves, the amplitude determines the amount of energy of the wave. More precisely, the energy with which a wave hits is equal to the amplitude squared. So, if you were standing on the beach and were hit by a water wave one foot tall, little would happen. But if it were two feet tall, the wave would have four times the impact . If it were four feet tall, it would have 16 times the impact . If the wave were as tall as a tsunamiwell, you know what would happen then.

This relationship between amplitude and energy holds true for any wave that requires a material medium. These are classical waves they can be described by Newtons Laws of Motion. However, the relationship between amplitude and energy does not hold true for quantum waves. Quantum waves do not require a material medium and do not follow Newtons Laws of Motion. Rather, they follow the laws of the quantum world.

Applications Of Amplitude Modulation

1. Air band radio: The amplitude modulation is extensively used in aerospace industry. The VHF transmissions made by the airborne equipment still use amplitude modulation. The radio contact between ground to ground and also ground to air use amplitude modulated signals.

2. Broadcast transmission: Amplitude modulation is still widely used for broadcasting either short or medium or long wave bands.

3. Quadrature amplitude modulation: Amplitude modulation is used in the transmission of data of almost everything, from short-range transmission such as wifi to cellular communications. Quadrature amplitude modulation is formed by mixing two carriers that are out of phase by 90°.

4. Single sideband: The amplitude modulation in the form of single sideband is still used for HF radio links.

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Modulation Index Or Modulation Depth Examples

The maximum amplitude of the message signal must be less than the maximum amplitude of the carrier signal to avoid any distortion in the modulated signal. For example, if the carrier signal amplitude is 5 volts then the message signal amplitude must be less than 5 volts. Hence, the maximum value of the modulation index will be less than one or equal to one when Am < = Ac. The minimum value of the modulation index will be zero.

Based on this, there are three types of modulation:

1. Perfect-Modulation

3. Over-Modulation

Amplitudes Of Quantum Waves Determine Probabilities

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Instead of determining energy level, the amplitude of a quantum wave determines probabilities. For example, where wave amplitudes are calculated as higher, the associated particle is more likely to be detected. Specifically, the likelihood of detecting the particle in a particular position is equal to the square of the amplitude in that location.

The amplitude of a quantum wave is also called the probability amplitude. When the probability amplitude is squared in order to calculate actual probabilities, it is called the probability density. 1

A key feature of the quantum world is that the behavior of quantum particles is not deterministic as in the everyday world of tables and chairs. The behavior of quantum particles is, instead, probabilistic.

Probability density of the distance of the electron from the nucleus of a hydrogen atom. Vertical axis is probability horizontal axis is distance from the nucleus.

It may seem surprising that the amplitude of quantum waves has a different physical implication than the amplitude of classical waves that create ripples in matter. However, the term wave is used in quantum physics only on analogy with the classical waves that we see in everyday life quantum waves are not at all the same beast as everyday waves.

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Calculation Of Modulation Index From Amplitude Modulated Waveform

The below figure shows the amplitude modulated waveform through which we can calculate the modulation index.

It is clear from the below figure that the modulating signal rides above the carrier signal.

From the above figure, we can write,

The above equation gives the technique of calculating modulation index from amplitude modulated wave.

What Is The Amplitude Equation For A Wave

The amplitude formula for a wave is amplitude = distance traveled by the wave / frequency of the wave . The amplitude is the maximum height observed in the wave. Amplitude is measured in decibels .

Amplitude of a wave is how big the wave is or the energy of the wave. It is measured by the depth from the equilibrium point to the lowest point of a trough or the height from the equilibrium point to the highest point of a crest. The trough is the part of the wave that slopes downward, and the crest is the part of the wave that points upward.

Wavelength is the length of a wave from one crest to another or from one trough to another. It is measured in metres.

The frequency measures how many waves are passing a point per second and is the inverse of time. Frequency is measured is Hertz . The frequency is derived by 1 / T where T is the period of time. For example: if a pendulum takes 5 seconds to swing back and forth, then frequency is 1 divided by 5.

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How Does Amplitude Affect The Motion

The restoring force that emerges is directly varied to the amplitude of motion.

The rise in amplitude leads to an increase in the force, which further increases the acceleration. The amplitude does not have any effect on the frequency and angular frequency. Therefore amplitude does not affect the motion.

Advantages Of Amplitude Modulation

Definition of Amplitude and Period | Physics | Khan Academy

1. Few components needed: At the receiver side, the original signal is extracted using a circuit consisting of very few components.

2. Low cost: The components used in amplitude modulation is very cheap. So the AM transmitter and AM receiver build at low cost.

3. It is simple to implement.

4. Long distance communication: Amplitude modulated waves can travel a longer distance.

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Frequency Spectrum Of Amplitude Modulation

The carrier is an un-modulated sinewave which has a single value of frequency and carries no useful information. When such a carrier is modulated with a message signal, other frequencies can be detected in it. These new frequencies that are caused by modulation are called sidebands. These sidebands are created above and below the carrier frequency.

The sidebands that are created above the carrier frequency are called upper sidebands and the sidebands that are created below the carrier frequency are called lower sidebands.

I.e. fUSB = fc + fm and fLSB = fc fm

Where, fc is the carrier frequency

fm is the message signal frequency

fLSB is lower sideband frequency

fUSB is upper sideband frequency

To see how it works, take the example of a carrier of 800 kHz frequency which is modulated by a message signal of 10 kHz frequency. The process of modulating a carrier signal with message signal is same as mixing two signals together. As a result of modulation, two sideband frequencies are produced.

One sideband frequencies are created above the carrier frequency. These sidebands are known as upper sidebands or sum frequencies. The upper sidebands are created due to the addition of carrier signal frequency with the message signal frequency I.e. 800 kHz + 10 kHz = 810 kHz.

I.e. 10 kHz frequency is produced above and below the carrier.

Consider the expression of AM wave given by equation


a = sin ct

= Ac sin ct

Difference Between Amplitude And Magnitude

Amplitude vs Magnitude





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Module : Sensation And Perception

  • Describe important physical features of wave forms
  • Show how physical properties of light waves are associated with perceptual experience
  • Show how physical properties of sound waves are associated with perceptual experience

Visual and auditory stimuli both occur in the form of waves. Although the two stimuli are very different in terms of composition, wave forms share similar characteristics that are especially important to our visual and auditory perceptions. In this section, we describe the physical properties of the waves as well as the perceptual experiences associated with them.

Frequency Wavelength Amplitude And Wave Speed

Will this Radio Frequency Oven Change How We Cook Food ...

You need to know about these quantities used in waves – what they mean, the symbols used for them and the units used to measure them.

The amplitude ) of a wave is the distance from the centre line to the top of a crestor to the bottom of a trough. Be careful with this quantity – the centre line is not always given in a diagram. Amplitude is measured in metres ). The greater the amplitude of a wave then the more energy it is carrying.

The wavelength, \, of a wave is the distance from any point on one wave to the same point on the next wave along. To avoid confusion, it is best to measure wavelength from the top of a crest to the top of the next crest, or from the bottom of a trough to the bottom of the next trough. Wavelength is also measured in metres ) – it is a length after all.

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What Does Amplitude Mean For Kids

Amplitude isisamplitude

. Similarly, it is asked, what is the simple definition of amplitude?

Amplitude, in physics, the maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. It is equal to one-half the length of the vibration path.

Subsequently, question is, what is an example of amplitude? noun. The definition of amplitude refers to the length and width of waves, such as sound waves, as they move or vibrate. How much a radio wave moves back and forth is an example of its amplitude.

Beside this, what is amplitude of a wave?

The amplitude of a wave refers to the maximum amount of displacement of a particle on the medium from its rest position. In a sense, the amplitude is the distance from rest to crest. Similarly, the amplitude can be measured from the rest position to the trough position.

What is frequency in simple words?

Frequency describes the number of waves that pass a fixed place in a given amount of time. So if the time it takes for a wave to pass is is 1/2 second, the frequency is 2 per second. The hertz measurement, abbreviated Hz, is the number of waves that pass by per second.

What Is Period Of Sound

A period can be said to be the time taken to do something. If an event occurs repeatedly then the event is said to be periodic. The time taken by the periodic event to repeat itself is known as the period. The time taken by the particle to complete one vibration cycle is the time period for that particle.

Period = 1/Frequency

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What Is Amplitude Formula

Amplitude refers to the maximum change of a variable from its mean value. The amplitude formula helps in determining the sine and cosine functions. Amplitude is represented by A. The sine function cosine function can be expressed as,

x = A sin or x = A cos


  • x = displacement of wave
  • A = amplitude

Amplitude Wavelength And Frequency

Finding the Amplitude | Waves | Physics

Learn about how waves are measured according to amplitude, wavelength and frequency.

The frequency of a wave can also be calculated using this equation:


f = frequency = number of waves produced by a source per second, in hertz Hz.

T = period = time it takes for one complete vibration or oscillation, in seconds s.

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What Is The Motion Of Surface Waves

A surface wave is a wave that travels along the surface of a medium. Ocean waves are the best-known examples of surface waves. In a surface wave, particles of the medium move up and down as well as back and forth in an overall circular motion. The particles dont actually move closer to shore as the waves pass through.

Quantumamplitudes Expressed With Imaginary Numbers

Often quantum waves have amplitudes that must be expressed with imaginary numbers.

A note to define imaginary, real, and complex numbers : An imaginary number is one that includes the square root of -1, written . What number multiplied by itself, that is, squared, equals -1 ? No ordinary number fits the bill. Its an imaginary number. Nevertheless, we can write it

can also be written as i . An entire set of imaginary numbers can be created by multiplying i times a regular number, for example: 3i 4 ½ i -7.35 i

Imaginary numbers have proved very useful in both math and physics.

Often, when we describe the physical universe, we use ordinary numbers, called real numbers. These are all the numbers that could be used to express distances measured by a ruler:

0, 1, 4 ½, 7.9543 -1, -2 ¾, -5.6983


3 + i -14 + 4i 5 2.7i

The combination of both real and imaginary numbers is called a complex number.

Back to amplitudes. Often the amplitude of a quantum wave is expressed as a complex number, that is, it has both a real part and an imaginary part. When the amplitude is used to calculate the probability of detecting an electron or other particle in a particular position, the amplitude is squared.


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Disadvantages Of Amplitude Modulation

1. Amplitude modulation is inefficient in terms of its power usage: As we know that the message signal contains information whereas the carrier signal does not contain any information. In amplitude modulation, most of the power is concentrated in the carrier signal which contains no information. At the receiver side, the power consumed by the carrier wave is wasted.

2. It requires high bandwidth: The amplitude modulation is not efficient in terms of its use of bandwidth. It requires a bandwidth equal to twice that of the highest audio signal frequency.

3. This type of transmission can be easily affected by the external radiation.

4. This type of transmission is also affected by the man-made noises or radiations like waves from other antennas or channels.

5. Amplitude modulation cannot be used for transmitting music as done by frequency modulation .

6. Amplitude modulation cannot be used for transmission of sensitive information like in the army, where interpretation or loss or disruption during transmission is not an option.

Amplitude Period And Frequency

Amplitude of sound?

Here is a ball moving back and forth with simple harmonic motion :

Its position \ as a function of time \ is:

\ = A \cdot \cos \Bigl\)

where \ is the amplitude of motion: the distance from the centre of motion to either extreme

\ is the period of motion: the time for one complete cycle of the motion.

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What Is Amplitude Of Sound

The amplitude of a sound wave is the measure of the height of the wave. The amplitude of a sound wave can be defined as the loudness or the amount of maximum displacement of vibrating particles of the medium from their mean position when the sound is produced. It is the distance between crest or trough and the mean position of the wave.

Loudness is directly proportional to the amplitude of the sound. If the amplitude of a sound wave is large, then the loudness of sound will be more. If the amplitude is small, then the sound will be feeble.

Define Amplitude In Physics

The amplitude which is the peak-to-peak amplitude that is the abbreviated pp is the change between peak that is the highest amplitude value. The lowest amplitude value can be negative as well. Sp with appropriate circuitry we can say that the peak-to-peak amplitudes of electric oscillations can be measured by meters or by viewing the waveform on an oscilloscope. The p-p or the peak-to-peak amplitude is a straightforward measurement on an oscilloscope. That way we can say the peaks of the waveform are easily identified and measured against the graticule. This generally remains as a common way of specifying amplitude but sometimes we can say that the other measures of amplitude are more appropriate.

For alternating current electric power generally, the universal practise is to specify RMS values of a sinusoidal waveform.

Q1. Explain Amplitude and Frequency.

Ans: For the term waves these variables have the same basic meaning we can say that. The term that is amplitude which is the distance between the resting position and the maximum displacement of the wave. The term that is frequency is said to the number of waves passing by a specific point per second. And the term period is defined as the time it takes for one wave cycle to complete.

Q2. Explain What is Amplitude in Physics Class 8.

Q3. What is the Amplitude of the Signal?

Q4. How is Amplitude Expressed in Units?

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