How To Measure Wavelength With A Ruler

The beneath video shows yous a thin movie experiment and measurement, much like the one on the residual of this folio.

Audience
10th, 11th, 12th grade science

Time Frame: 60 min menstruum or less depending on how long it takes for the required content earlier the activity
Set-up:
Activity 1: (v min)

Objective(s)
After completing the action, participants will be able to:

1. Explain that X-Ray reflectometry is a tool used to measure out the thickness of a thin pic.
2. Identify applications where sparse films play an important role.
3. Employ mathematical formulas when to calculate experimentally the thickness of a thin film made of nail polish using the wavelength of light as a ruler.
4. Understand that our vision and physical tools take limitations

Standards Addressed
Side by side Generation Science Standards PS 4

1. Construct explanations for why the λ of an electromagnetic wave determines its employ for certain applications
2. Make inferences and justify conclusions from sample experiments
3. Clarify that multiple technologies are based on the agreement of waves and their interactions with affair are everyday experiences in the modern globe
4. Reason quantitatively and employ units to solve problems

National Science Education Content Standards

• Students relate and apply concepts of energy and its interaction with matter to recognize types of waves and explain how they transfer energy, and to explain how wavelengths can exist used to identify samples of matter.
• Students dispense, communicate and present data using appropriate statistics, mathematical models, and bachelor engineering

Engineering principles
Course Band Terminate Points for ETS2.B
Past the cease of class 12. Modern civilization depends on major technological systems, including those related to agriculture, health, water, energy, transportation, manufacturing, construction, and communications. Engineers continuously modify these technological systems by applying scientific noesis and applied science design practices to increase benefits while decreasing costs and risks. Widespread adoption of technological innovations often depends on market forces or other societal demands, but it may also be subject to evaluation by scientists and engineers and to eventual government regulation. New technologies tin can accept deep impacts on order and the environment, including some that were not anticipated or that may build up over time to a level that requires attention or mitigation. Analysis of costs, environmental impacts, and risks, as well as of expected benefits, is a disquisitional aspect of decisions virtually engineering science use.

Action Materials
Part 1(Groups of two) Each group volition demand the following:
A pocket-sized round bowl with a flat surface or glass/plastic Petri dishes. A slice of thin copper wire effectually 9 inches (23 cm).Water to cover the wand in the basin or Petri dish and ONE drop of clear nail shine.

Part 2(Groups of two) A half-dozen by six in. piece of black poster lath, a flat plate or pan to place poster lath, h2o to immerse the poster board, ONE drib of transparent nail polish, one red LED flashlight and one green LED flashlight, scissors, two colored pencils or pen, tape and white paper.

Activeness Instructions
Ready-up: ten minutes setting up and conducting part 1

Part 1- The first activity is part of the lesson plan. Students will make a thin film and effort to fish information technology out and observe any color interference that would be an indication of a thin flick. Through open word, students realize that you cannot get too much data about the thin film if it does not take a substrate to identify the sparse pic on it.

Procedure for Role 1

Introduction (see background information) xxx minutes
Function 2 of the Action (10 min)

Place black paper in a tray and cover it with the smallest amount of water.

Brand sure the paper is completely under h2o.
Add one drop of smash polish and wait approximately 1 minute to remove it slowly by the ends.
(Do not let the picture show slip from the paper.)
Let it dry
NOTE: In order to save time, the teacher can requite out other thin film prints already fabricated that are dry so the quantitative part of the activity can keep.
The results should expect like this:

The discussion should lead to the fact that since white light has all the wavelengths, white lite is non a good "ruler" to measure how thick the thin movie is.

At present, the moving picture volition be exposed to specific lights that have specific wavelengths. Starting time with the red and count the Night fringes that you encounter. Record this number. The dark fringe is where destructive interference occurs. Repeat the process with the green light. If done carefully, the students volition find that for every iv red fringes, there will exist v fringes with the utilise of the dark-green lite. This is why it is important to make the sparse picture printout to be used, with many rings. If you lot have less than 4 fringes of red, the green will besides be the aforementioned corporeality. The platonic situation to observe the trend is being able to brand thin films that you tin can see eight fringes with the carmine light and ten with the light-green light. This can be the students' independent research; to make a sparse film that shows this effect. The reason for this difference is that green light has a shorter wavelength than cherry so this "ruler"can be more accurate. Make certain that the same section is observed and then proper comparisons can be made.

The introduction to the tabular array below should be discussed with the students:

Where practice the nighttime fringes come from?

Light reflects from surface and from the lesser.

In order for the waves to exist out of stage, at that place is a difference in path of λ/2. If the waves are in phase, constructive interference occurs. The night fringes are a outcome of destructive interference.

The tertiary role of the activity (v min)

This activity will show that there is a difference in the view of the sparse film fringes under ii different colors of light.
Instructions: Meet diagram beneath

The post-obit picture shows the same thin film nether the different lights. Discover that the fringes are non exactly seen at the same position. The reason for this is that the wavelength of green light is shorter that the wavelength of scarlet.

The 4th Part of the Activeness (10 min)

This is the part where the students volition calculate the thickness of the flick using the information collected when counting the dark fringes with the ruby lite and the green calorie-free.

Thickness (t) = # dark fringes ( λ/2)
Example: red : counted iv fringes. λ for cherry light through plastic is 458 nm
t= 4 x λ/ii
t= (4) 458/ two = 916 nm with red light
Case: light-green: counted 5 fringes. The λ for dark-green low-cal through plastic is 366 nm
t= (5) 366/2 = 915 nm
This is just an instance if you actually see these numbers of fringes. Retrieve that a educatee tin go the same corporeality of fringes if the proportion is not 4 to 5 equally explained earlier. This is where analyzing the results of all the group is of great benefit if a group sees simply three.

Conclusion ( 5 min)
In decision, nosotros accept a ruler as accurate as λ/two

Discussion on how could we be more accurate? Past using a "ruler" with a very short wavelength such as X-Ray Reflectometry. X-Rays have a wavelength of 1.5 Å that is equivalent to 0.15 nm; a thousand times better ruler!

Assessment

1. Name four applications for thin films
2. Why are thin films necessary? What are the limitations of our vision in determining thickness?
3. iii. What can exist a amend ruler to mensurate the thickness of a thin layer and why?
4. What would we demand to know in gild to make up one's mind the validity of our data?
5. What tin can you conclude when analyzing the calculations made using two different lights?
6. Which light was a ameliorate ruler? Justify your answer
7. Provide an educated explanation in terms of what you think will happen if nosotros employ an LED blue flashlight for this activity. Pattern an experiment to exam your hypothesis.

Background

There should exist an introduction about the engineering known equally thin films. The major points about this topic are the following:

• What are thin films?
• Examples of common thin films
• Applications of sparse films
• Methods to build sparse films
• How is the thickness of thin films measured and why is information technology of import to know it?

Concepts that need to be adult if not known yet:

• The relation betwixt wavelength and color
• Visible lite wavelength range
• Thin picture show interference
• Constructive and destructive interference
• Index of refraction
• Stage change and λ / 2
• Basic law of reflectivity

The post-obit diagram helps in explaining when you see fringes in a thin picture show

When ray ane hits the surface on the height, some of the light is partially reflected equally seen in ray2 and the rest is refracted as seen in ray 3. When ray 3 hits the bottom surface, some of it is reflected as seen in ray 4 and the rest is refracted as seen in ray 6.

When ray 4 hits the top surface from underneath some is reflected and some is refracted every bit seen in ray five

Figuring out the path length deviation that the surface reflected ray takes and the internal reflected ray can make up one's mind the thickness of the film that will crusade a detail λ of light to exist reflected.

References
Interference: Thin motion picture interference and reflection. (n.d.) In Physclips. Retrieved July 10, 2013, from http://www.animations.physics.unsw.edu.au/light/interference/

Physical eyes Thin film Interference. (north.d.) In Physical Optics. Retrieved July 10, 2013, from http://dev.physicslab.org/Document.aspx?doctype=3&filename=PhysicalOptics_ThinFilmInterference.xml

Thin Moving-picture show Interference. (due north.d.). In Physiscs Classroom. Retrieved July x, 2013, from http://world wide web.physicsclassroom.com/Class/calorie-free/u12l1c.cfm

What Wavelength Goes with Color? (n.d.). In National Helmsmanship and Infinite Administration. Retrieved July 10, 2013, from http://science-edu.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html

Authors
Evelyn Montalvo, RET teachers
MRSEC IEG Leadership Team: Ben Taylor, [ Paul Evans, Margaret Cosgriff, and Anne Lynn Gillian-Daniel.

Source: https://education.mrsec.wisc.edu/using-the-wavelength-of-light-%CE%BB-as-a-ruler-to-measure-the-thickness-of-a-thin-film/

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