How do I determine the number of fringes in Thermal Expansion Lab?

In summary, the conversation is about a thermal expansion lab and the steps involved in completing the prelab question. The first step is to find the change in length of a copper bar as it cools from 50 to 22 degrees using the expansion coefficient of copper. The second step involves finding the number of fringes observed during this process, which can be determined using the relationship between change in length and wavelength. The last step is to understand the relationship between relative changes in length and changes in intensity.
  • #1
ricola_pak
4
0
Thermal Expansion Lab

I'm trying to do the Prelab question 2 in the above lab.

These are the steps I'm taking, please correct me if I am wrong, and please assist me where I need help, thanks!

1) The expansion coefficient of copper is 16.7*10^-6 K^-1, and the length of the bar of copper is 0.15m. To find out how much the bar contracts as it cools from 50 to 22 degrees, do I simply multiply the coefficient by (50-22) and multiply this to the length of the bar?

2) Now, to find out how many fringes I will see as this process occurs, what should I do?

In the first step I have obtained delta L, the change in length of the bar. I also know the relationship delta L = wavelength/2. So I can find out the wavelength, but how does that tell me how many fringes I will be seeing?

3) On the bottom of page 1, it says that the relative changes in length will result in changing the intensity from zero to twice of the original beam... I am not too sure where I can see this relationship?


Thanks a lot!
 
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  • #2
For the first part,i'm sure the formula that u have to use is

[tex]l_{T}=l_{T_{0}}\left[1+\alpha \left(T-T_{0}\right)\right] [/tex]

Daniel.
 
  • #3
Thanks Daniel. Can anyone else help me to relate this to how many fringes I should observe?
 

FAQ: How do I determine the number of fringes in Thermal Expansion Lab?

1. What is the purpose of the Thermal Expansion Lab?

The purpose of the Thermal Expansion Lab is to observe and measure the expansion of different materials as they are heated and cooled. This allows for a better understanding of how thermal energy affects the size and shape of objects.

2. How do you conduct the Thermal Expansion Lab?

To conduct the Thermal Expansion Lab, you will need a sample of the material being tested, a thermometer, a heating source, and a ruler or caliper for measurements. The material is heated and its length is measured at different temperatures. The process is then repeated while cooling the material to observe changes in length.

3. What factors affect thermal expansion?

The main factors that affect thermal expansion are the type of material, its composition, and the temperature change. Different materials have different coefficients of thermal expansion, which determine how much they will expand or contract with temperature changes. The composition of the material also plays a role, as materials with a higher percentage of certain elements may expand more. Finally, the magnitude of the temperature change will also affect the amount of thermal expansion.

4. Why is thermal expansion important to study?

Studying thermal expansion is important for several reasons. It helps us understand how materials behave under different temperatures, which is crucial for engineering and construction. It also has practical applications in areas such as thermometers, thermostats, and expansion joints. Additionally, thermal expansion is a fundamental concept in materials science and thermodynamics, and studying it can lead to further advancements in these fields.

5. What are some real-world examples of thermal expansion?

There are many real-world examples of thermal expansion, including the expansion of metal bridges and railroad tracks on hot days, the cracking of pavement due to temperature changes, and the behavior of liquids in thermometers. Other examples include the use of bi-metallic strips in thermostats and the design of expansion joints in buildings and bridges to allow for thermal expansion without structural damage.

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