Simulation link: https://vlab.amrita.edu/repo/PHY/OPT/CornusMethod/CornusMethod.swf
Procedure
![](/userfiles/1/image/cornus2.JPG)
1. Real lab
To find the diametre of rings without mass
- Place the given Perspex beam symmetrically over the two knife edges.
- A convex lens is placed over beam.
- As shown in figure light is allowed to fall normally on the air film with the help of glass plate.
- On focusing, interference fringes formed are viewed by means of travelling microscope.
- Fix the cross wire on any of the nth ring on one side (left or right) using the knob.
- Corresponding value of MSR and VSR is noted.
- Move the cross wire to the (n-1)th or (n-2)nd ring on the same side.
- Take the readings of the rings on either side of the centre position.
- Now repeat the same procedure by moving the cross wire up and down on either side of centre position.
![](/userfiles/1/image/cornus(1).jpg)
Diametre of rings with mass
- Adjust the distance between the weight hanger and the knife edges.
- Add mass on the weight hanger.
- Repeat steps 4-9 to measure the horizontal and vertical position of rings.
2. Simulator
To find the diametre of rings without mass
- Mass on weight hanger is set as zero g.
- Select desired values for the variables by clicking on the sliders for each variable.
- Click on the ‘Light On’ button.
- Now the repeat the steps 5-9 of real lab.
- The reading of rings during the horizontal/vertical motion is shown by the horizontal/vertical position value of microscope under variables section.
- Click ‘Reset’ button for another values of variables
To find the diametre of rings with mass
- Adjust the variables and position of weight hanger by clicking on their corresponding sliders.
- Add suitable mass on weight hanger.
- Repeat steps 3-6 of simulator.
Observations
To find the thickness of Perspex beam using screw gauge
Zero correction=
![](/userfiles/1/image/cor tabl1.JPG)
Thickness of Perspex beam, b=………..mm
To find the breadth of Perspex beam using Vernier calipers
![](/userfiles/1/image/corn tabl 2'.JPG)
Breadth of plate, a=…………cm
To find the diameter of rings in horizontal direction
λ=………..nm, l=………cm
![](/userfiles/1/image/corntable3'.JPG)
Longitudinal bending R1 = ![Double click to edit «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mfrac»«mn»1«/mn»«mrow»«mn»4«/mn»«mi»n«/mi»«mi»§#955;«/mi»«/mrow»«/mfrac»«mfrac»«mrow»«msub»«msup»«mi»d«/mi»«mrow»«mo»§apos;«/mo»«mn»2«/mn»«/mrow»«/msup»«mi»n«/mi»«/msub»«msub»«msup»«mi»d«/mi»«mn»2«/mn»«/msup»«mi»n«/mi»«/msub»«/mrow»«mrow»«mo»(«/mo»«msub»«msup»«mi»d«/mi»«mn»2«/mn»«/msup»«mi»n«/mi»«/msub»«mo»-«/mo»«msub»«msup»«mi»d«/mi»«mrow»«mo»§apos;«/mo»«mn»2«/mn»«/mrow»«/msup»«mi»n«/mi»«/msub»«mo»)«/mo»«/mrow»«/mfrac»«mo»§nbsp;«/mo»«mo»§nbsp;«/mo»«mo»§nbsp;«/mo»«mo»§nbsp;«/mo»«mo»§nbsp;«/mo»«mo»§nbsp;«/mo»«/math»](/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=9704aaf1ac7f70bba5b16ea1e2933f36.png)
To find the diameter of rings in vertical direction
![](/userfiles/1/image/corntabl3.JPG)
Lateral strain, R2 = ![Double click to edit «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mfrac»«mn»1«/mn»«mrow»«mn»4«/mn»«mi»n«/mi»«mi»§#955;«/mi»«/mrow»«/mfrac»«mfrac»«mrow»«msub»«msup»«mi»d«/mi»«mrow»«mo»§apos;«/mo»«mo»§apos;«/mo»«mn»2«/mn»«/mrow»«/msup»«mi»n«/mi»«/msub»«msub»«msup»«mi»d«/mi»«mn»2«/mn»«/msup»«mi»n«/mi»«/msub»«/mrow»«mrow»«mo»(«/mo»«msub»«msup»«mi»d«/mi»«mn»2«/mn»«/msup»«mi»n«/mi»«/msub»«mo»-«/mo»«msub»«msup»«mi»d«/mi»«mrow»«mo»§apos;«/mo»«mo»§apos;«/mo»«mn»2«/mn»«/mrow»«/msup»«mi»n«/mi»«/msub»«mo»)«/mo»«/mrow»«/mfrac»«mo»§nbsp;«/mo»«mo»§nbsp;«/mo»«mo»§nbsp;«/mo»«mo»§nbsp;«/mo»«mo»§nbsp;«/mo»«mo»§nbsp;«/mo»«/math»](/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=aa71a4f1c33fc81103220221073514dd.png)
Results
For a given plate
- Young’s modulus, Y=………………Nm-2
- Poisson’s ratio, σ =…………………
- Bulk modulus, b =………………….. Nm-2