PASCO OS-8170A Brewster’s Angle Accessory - Manual (Page 17)

®
Model No. OS-8170A Brewster’s Angle Accessory
17
®
The Curve Fit dialog box for the
green laser shows the coefficients of
the quadratic formula of the curve fit.
Questions
1. From the curve fit, how do you determine the minimum of the function?
To find the minimum, set dy/dx equal to zero
for the quadratic formula
.
Solving for x gives 55.9°.
To estimate the error, use the cursor in the
Graph display to select a different set of data
points (see the Graph).
The different set of data points gives an angle
of 56.1°.
The error estimate is 55.9°±0.2°.
2. Use Brewster’s Angle to calculate the index of refraction of the acrylic “D” Lens using
Equation (3): tan
p
= . What value should you use for n
1
?
The value of n
1
= 1.00 (for air).
for the green laser (wavelength = 532 nm)
for a blue diode laser (wavelength = 405 nm)*
(*See the sample data at the end of this section.)
Curve Fit dialog box for green laser
dy
dx
------ 2Ax B + 2 0.00127
  0.142
– 0 = = =

n
2
n
1
------
n
2
n
1

p
tan 1.00
 
55.9
  
tan 1.48 0.01

= = =
n
2
n
1

p
tan 1.00
 
57.3
  
tan 1.56 0.01

= = =