Bending light for microscopic measurement

Posted: Feb. 5, 2013

What does it mean to win by a hair? A group of Mukwonago High School Advanced Placement students in Kristin Michalski's class recently used a laser to determine the slim margin provided by winning by a hair.

Building off a November visit to the University of Wisconsin-Milwaukee Raicu Lab, where students performed measurements on a Two-photon microscope, the students expanded their understanding of the structure of matter at the microscopic level and how researchers see very small structures. During that visit students learned the safety precautions needed when using powerful lasers. They learned why certain microscopes are suited for different structures such as proteins or bacteria. They also learned how to prepare microscope slides with fluorescent samples before capturing the image with a Two-photon microscope, Michalski explained.

The fluorescent sample was used to show students how the microscope measures the photon emission spectrum and how it is used to calibrate the microscope, according to Michalski.

The students also analyzed some data to gain understanding of how light is distorted by the microscope so they can compensate for this when analyzing data when imaging living structures.

With this background information, students taped human hair to a mounting bracket, lined up a laser on top of a wood block and aimed the light at the hair until a pattern of diffracted light appeared on a white paper background.

As they worked through the lab on human hair, their visit to the UW-Milwaukee became a bit clearer.

While the UW-Milwaukee lab visit was a bit "hard to follow," Senior Taylor Geiger said, "I think I understand it better now."

Measuring the distance between bands of light diffracted by the hair - with thinner hair producing wider bands of light from the laser - students calculated the width of hair. To help determine the accuracy of their work, students confirmed if their measurement fell within the average range of width of human hair, which is 17 to 181 micrometers.

Visiting UW-Milwaukee and performing experiments at the college exposes students to "real science discovery," Michalski explained. The experience engages students as they make career choices and decisions about future studies beyond medicine and engineering. The opportunity allows students to learn how real scientists work and demonstrates the importance of research and the active role students can play in scientific research.

By working with real scientists, students get a glimpse of the people behind the microscopes, Michalski added. As students tackle the challenge of AP physics, hoping to earn some college credit, the university visit helps them connect what they are learning in class with current biophysical research.

The AP course may provide some students with a jump start on college, but for Lily Larson, who likes "all the Stephen Hawkings stuff" and is thinking of becoming a physicist, she's ready to dig beyond the "surface stuff."