Light from air to acrylic and acrylic to air

[spitzer89]

1. question
its a exercise where we have a acrylic block and we are going to send light though and wath how the refraction change the light direction. then we measure the ingoing and outgoing angels.

air to acrylic(sin(i) is outside the block and sin(b) is on the other side of the block)
acrylic to air(sin(i) is now inside the block and sin(b) is on the outside of the block still)

so we shoot light though the block two times and measures the angeles according to from air to acrylic and acrylic to air.

the angels are the put into excel with sin(i) on the y-axis and sin(b) on the x, then there's added a trendline and then you read the refractive value from the equtation of the trendline.

The Attempt at a Solution

well i made the ghaps in excel and i got these values

air to acrylic there i got 1,5 in refractive value with is what the Refractive index for acrylic is

acrylic to air there i got 0,3

now as far as is know the Refractive value is 1,5 and acrylic and should be that both times, so the question is what is i doing wrong in the second excirse from acrylic to air.

here is a image of something that reminds of our excise:
http://www.websters-online-dictionary.org/images/wiki/wikipedia/en/thumb/0/04/Refraction.jpg/250px-Refraction.jpg

here you can download my excel work with my data and graphs
http://www.4shared.com/file/l4oWxzwc/forsg_4.html

hope you guys can tell me why i get different values for the refractive value

 

[jbsteele]

in the two excersices. Answer:It is possible that the angle of incidence (i) or the angle of refraction (b) are not being measured correctly, resulting in inaccurate values being recorded. It is also possible that the trend line is not being generated correctly, resulting in an incorrect refractive index value. Check your measurements and make sure the trend line is properly configured to ensure accurate results.