# Wave propation -- Speed variation in different indices

• duchuy
In summary: This means that as light energy increases, its frequency also increases, but as light energy decreases, its frequency also decreases.
duchuy
Homework Statement
Speed variation in different indices
Relevant Equations
c = λ.f
Hi,
I have this question about the variation of wavelength and frequency as light travels to an environment with a different index.
As we have learned in class, celerity can change as light enters a different environment, however frequency and wavelenght are independent and remain constant (right?)
So if this is the case, and c = λ.f , I don't understand how celerity can change but λ and f remain constant? Are there different parameters that I have to take into account that I haven't?
Thank you so much for your help!

duchuy said:
As we have learned in class, celerity can change as light enters a different environment, however frequency and wavelenght are independent and remain constant (right?)
Nope, not right. Frequency remains constant, not wavelength.
duchuy said:
So if this is the case, and c = λ.f , I don't understand how celerity can change but λ and f remain constant?
Good! You knew something must be wrong somewhere.

Doc Al said:
Nope, not right. Frequency remains constant, not wavelength.

Good! You knew something must be wrong somewhere.
Ohh ok thank you so much!

Oh but there is still something bugging me )):.
In the electromagnetic wave spectrum, we can see that as wavelenght increases, frequency decreases and vice versa and in this case, celerity is unchanged.
So in this case, wavelenght and frequency changes due to the variation of energy and is this case what is the formula for this? I'm really struggling to see when certain variables change and when they don't...

duchuy said:
In the electromagnetic wave spectrum, we can see that as wavelenght increases, frequency decreases and vice versa and in this case, celerity is unchanged.
Right. The speed of light in a vacuum is the same for all frequencies.

duchuy said:
So in this case, wavelenght and frequency changes due to the variation of energy and is this case what is the formula for this?
A photon's energy relates to its frequency like so: ##E = h f##, where ##h## is Planck's constant.

duchuy

## 1. What is wave propagation and how does it relate to speed variation in different indices?

Wave propagation is the movement of energy through a medium, such as air, water, or solid materials. The speed of propagation is affected by the physical properties of the medium, such as density and elasticity. Different indices, or measures of a medium's properties, can cause variations in the speed of wave propagation.

## 2. How does the speed of wave propagation vary in different mediums?

The speed of wave propagation can vary greatly depending on the medium. For example, sound waves travel faster through denser materials, such as water, than through less dense materials, such as air. Similarly, seismic waves travel at different speeds through different types of rock and soil.

## 3. What factors can affect the speed of wave propagation?

The speed of wave propagation can be affected by several factors, including the density, elasticity, and temperature of the medium. Additionally, the frequency and wavelength of the wave can also impact its speed. In some cases, external forces, such as gravity or electromagnetic fields, can also influence the speed of wave propagation.

## 4. How is the speed of wave propagation measured?

The speed of wave propagation can be measured using various methods, depending on the type of wave and medium. For example, the speed of sound can be measured using a stopwatch and known distance, while the speed of seismic waves can be calculated using seismographs and the time it takes for the waves to reach different stations. In general, the speed of wave propagation is measured in meters per second (m/s).

## 5. What are some real-world applications of understanding wave propagation and speed variation?

Understanding wave propagation and speed variation is crucial in various fields, such as engineering, geology, and medicine. In engineering, knowledge of wave propagation is used to design and test structures to withstand seismic activity. In geology, it is used to study the Earth's interior and predict earthquakes. In medicine, it is used in techniques such as ultrasound imaging and shock wave therapy. Additionally, understanding wave propagation can also help in the development of new technologies, such as wireless communication and sonar systems.

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