Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Error bars represent 95% confidence intervals. Line of best fit has been included for the straight glass data and a curve of best fit has been included for the curved glass data.
