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General Resources:
General Resources:
Kognity Textbook Chap 4 - Use you ACS Login
IB Physics Site: Topic 4 - Comprehensive notes
IB Physics Site: Topic 4 - More notes
Topic 4 Flashcards - Vocab Devo.
Snell's law of refraction (or Abu Said al-Ala Ibn Sahl's Law?) is used to describe the relationship between the angles of incidence and refraction, when a ray of light (or other waves) passes through a boundary (or interface) between two different media, such as water, glass or air.
The refractive index of air is assumed to be 1, therefore if medium 1 is air then n1=1 so,
Snell's Law
Snell's Law
So, the refractive index of a medium can be determined from the gradient of a graph of sinθ1 (y-axis) against sinθ2 (x-axis).
Indicies of Refraction
Indicies of Refraction
Total Internal Refraction within a lucite right triangle.
Take a photo of your setup.
Using Geogebra, determine the angles of incidence and refraction.
Enter the values for your group's data into the sheet below.
Repeat your procedure for two more blocks of you choosing.
Light passing thru three media, compare the refractive index of the glass block to the lucite.
Snell's Law Class Data - Please open and add your data.
Bending Light - PhET Simulation
Bending Light - PhET Simulation
Double click on "More Tools"
1. Wavelength
1. Wavelength
Switch the laser on by clicking the red button.
Check the Angles box.
QUESTION: Observe any changes in the angle of refraction or the refractive index. What can you deduce about wavelength and refractive index?
Alter the wavelength by clicking and dragging on the wavelength pointer.
2. Wave Speed
2. Wave Speed
Drag the Speed tool over to the ray of light in air so that it points at the ray.
The reading shows 1.00 c, which means that the speed is 1.00 times the speed of light.
Now move the Speed tool to the refracted ray in glass and record the speed. Then change the material from glass to water.
Record the speed again.
QUESTION: What can you deduce about wave speed and refractive index?
3. Wavelength
3. Wavelength
Change the laser from Ray to Wave(front).
QUESTION: What do you notice about the wavelength of the light when it refracts?
Click on the Refractive index slider to alter the refractive index from 1.00 to 1.600.
QUESTION: What can you deduce about wavelength and refractive index?
Problem Sets
Problem Sets
IB Reflection and Refraction Problems.pdfSubmit for feedback
Refractive Indexes (indicies) - With alternative equipment
Refractive Indexes (indicies) - With alternative equipment
Apparatus
Light box apparatus, single slit mask, semi-circular acrylic block, semi-circular cuvette for water
Light box apparatus, single slit mask, semi-circular acrylic block, semi-circular cuvette for water
Instructions
Attach the acrylic block to the protractor so that the plane surface is perpendicular to the ray of light. Ensure that the single beam of light is lined up with the midpoint of the block. Rotate the protractor so that the ray of light refracts at the plane surface as shown below.
Notice that most of the light is refracted at the surface and enters the acrylic block at a different angle while a small amount of light is reflected back from the surface at an angle according to the law of relection, as shown below. The brightness of the reflected light depends on the angle of incidence.
The angle of incidence θ1 is measured between the incident ray and the normal with the angle of refraction θ2 measured between the refracted ray and the normal. Set the angle of incidence θ1 to 10°, as shown below, and record the angle of refraction θ2 in the acrylic.
Repeat for other distinct values of incident angle.
Analysis
Copy and paste the data for θ1 and θ2 into LoggerPro. When entering the labels and units, the symbol for theta (θ) and the symbol for degrees (º) can be inserted as shown below.
The default settings for angle units should be changed from radians to degrees by clicking on the File tab and choosing Settings For . . .
and then clicking on Degrees, as shown below.
Click on the Data tab and choose New Calculated Column. In the dialogue box that appears type in an expression for sinθ1 and sinθ2, as shown below.
On the graph of sinθ1 (y-axis) against sinθ2 (x-axis) choose Linear Fit to determine the refractive index of the acrylic block from the gradient of the line.
CHECK: Use, for example, the internet to find an accepted value for the refractive index of acrylic and compare it with your experimental value.
Extension
Extension
Replace the acrylic prism with the plastic cuvette for water. After the cuvette is attached, carefully fill the cuvette with water from a beaker.
Repeat the experiment as before to determine the refractive index of water.
CHECK: Use, for example, the internet to find an accepted value for the refractive index of water and compare it with your experimental value.
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