# Experimental Physics I: Final Presentation: Optical Trapping. Measuring the Boltzmann Constant. | Summary and Q&A

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November 1, 2018
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MIT OpenCourseWare
Experimental Physics I: Final Presentation: Optical Trapping. Measuring the Boltzmann Constant.

## TL;DR

This video discusses the process of extracting Boltzmann's constant using optical trapping and Brownian motion in a lab setting.

## Key Insights

• 💿 Optical trapping and Brownian motion are techniques used to extract Boltzmann's constant.
• ❓ Calibrating the instruments used in the experiment is crucial for accurate measurements.
• ❓ Laser heating and systematic errors can introduce uncertainties in the results.
• 👨‍🔬 Collaborative efforts and partnerships are essential for conducting successful experimental research.

## Transcript

RUMEN DANGOVSKI: Hi, everybody. I'm Rumen, and today I'll talk about three things: optical trapping, the Boltzmann constant, and Brownian motion. The goal of the lab is to extract Boltzmann's constant out of Brownian motion and there are two key components to think about. First one is the Boltzmann's constant, which is prevalent in different types ... Read More

### Q: Why is Boltzmann's constant important in various scientific fields?

Boltzmann's constant plays a crucial role in biophysics and thermodynamics, helping scientists understand forces at the cellular level and the equipartition theorem.

### Q: How do scientists measure Boltzmann's constant?

Different methods, such as measuring the speed of sound in argon gas or using optical trapping, are used to calculate Boltzmann's constant. Optical trapping involves using lasers to control the motion of particles.

### Q: What determines the motion of the trapped beads in optical trapping?

The motion of trapped beads is determined by the net gradient and scattering forces, which balance each other to create simple harmonic motion when the bead is pushed off-center.

### Q: What are the challenges and limitations in measuring Boltzmann's constant?

Challenges include calibration errors, heating from laser interactions with water, and statistical uncertainties in the experimental setup.

## Summary & Key Takeaways

• The lab focuses on extracting Boltzmann's constant by studying optical trapping, the Boltzmann constant, and Brownian motion.

• Optical trapping involves using lasers to control the motion of spherical glass beads.

• Brownian motion, generated by thermal collisions in water, is observed through the use of light trapping.