Name:
__________________________
Partners: __________________________
__________________________
Date: _____________
Period: _____________
__________________________
__________________________
Refraction of Light
Purpose:
To find an equation relating the angles a light ray makes with the ‘normal’ on either side of a
border between air and water.
** Warning:
This lab allows you work with a laser. THIS IS NOT A TOY. Lasers can cause permanent
blind spots in the human eye. If you are horsing around with a laser, you will receive a ZERO
for the lab, and face disciplinary action.
Dish alignment: Check to make sure the surface of the water in your
dish is EXACTLY at the midway line. If not,
adjust it accordingly.
To collect data, turn the laser on. Adjust the slider so that the laser is at
the zero position at the top, pointing straight down into the water. Use
the markings at the bottom to determine the angle the laser makes
with the normal in water. Record this in the data table as w.
normal
a
air
water
Move the slider 5 degrees to the left. The laser is now moving through
the air at 5 degrees to the normal, this is the air angle.
w
Observe the change in direction of the laser line. Use the markings on
the bottom of the dish to determine the angle the laser is making with
the normal as it moves through the water. This is the water angle(w).
Record this value in the data table. Yes, you will need to estimate the
water angle if it does not fall exactly on a degree line.
REMEMBER:
You are measuring the angle relative to the NORMAL LINE.
Increase the air angle by 5 degree increments to the left and record the new water angle each time, up to 80
degrees. Calculate and record the SIN w and SIN a in your data table. Set your calculator to degree mode!
Now, move the slider to 0 degrees below the water so that the laser is pointing straight up. Move the slider left
to 45 degrees. Record what you see.
Move the slider a little further left to 60 degrees, you should notice a difference in the behavior of the laser.
Record what you see.
Now move the slider to the exact angle between 45-60 where the behavior of the laser changes.
Record this incident angle:
c =__________
This is known as the critical angle.
Air Angle
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
SIN(a)
Water Angle
SIN(w)
Look at your data table. Which angle is consistently larger as measured from the normal?
Air angle /
Water angle
Use the data to create a graph using a classroom computer and the Graphical Analysis Software.
Place the SIN of the air angle on the vertical axis, and the SIN of the water angle on the horizontal axis. Be
EXTREMELY careful not to mix up the columns when transferring your data onto the computer. Put all of the
data on one graph. Your team will create, print, and turn in one graph with this lab. On your team’s graph:
1. Properly label the column headings of data table, and axis labels of the graph. To change these labels,
double click each column heading box at the top of the data table. Type the proper column label in the
‘Name’ text field in the ‘Column Options’ popup window and click OK. This should change your graph
axis labels as well.
2. Transfer all the left and right side data in order to plot your graph. I will be checking to see if the data
on your electronic data table matches the data above, so make sure all the data is visible before you
print. Again, DON’T mix up the columns when transferring your data onto the computer.
3. Select the data you wish to analyze on the graph with the mouse and use the ‘Linear Fit’ button
to calculate the slope of your graph. (Note: you may need to uncheck the ‘Connect Lines’ box in
the ‘Graph Properties’ window. Double click anywhere on the graph to open this window.)
4. Type in your team number and team member names in the ‘Notes:’ textbox below the data table.
5. Click on the file menu, select ‘Page Setup’ and choose ‘Landscape’ as your graph’s orientation.
6. Get your graph approved by your instructor BEFORE printing. You only need one printed copy for
your team. Make sure the printer is set to GBW-RM-317.
7. Finally, write the equation for the line on the printed graph.
(Remember to use proper variables! NO ‘x’ and ‘y’ in your equation of the line!! I mean it!!!)