Lab 5: Lockin Amplifier Light Detection

PHYS 471, Spring 2026

In this lab, we will learn how to measure low light levels using a Lock-In Amplifier.

This lab consists of 1 Exercise and 1 Experiment

Exercise 1

This exercise is intended to make sure you can operate the SRS 830 Lock-In Amplifier. You will make a known signal using the function the generator and confirm that your measurement in the Lock-In is correct.

  1. Use the function generator to generate 400 Hz Sine wave.
  2. Connect the oscilloscope to monitor the output.
  3. Set the amplitude of the output to be 0.1 V RMS by measuring the wave on the oscilloscope.
  4. Connect the TTL output of the function generator to the REF IN of the Lockin.
  5. Using the T-Connector, also send the sine wave output to the A input channel on the lockin.
  6. Adjust the settings of the Lock-In until you can measure the 100 mV, 400 Hz signal.
  7. Use the Auto-Phase button to set the phase of the Lock-In so that the signal shown is predominately in the X channel.

Exercise 1 Set Up

Experiment 1

Measure the single slit interference pattern and confirm the spacing of the diffraction peaks match the theoretical expectations. Instructions will be presented in class.

Don't neglect to get a ruler to measure the distance between the slit and the detector plane. The parameters of the slit are written on the slit slide.

Here is a section from Fundamentals of Physics about calculating the intensity profile for a single slit diffraction pattern: intensity-single-slit-HR.pdf

Report to submit:

Please type up a short report that shows your measurements.

Due May 18, 2 pm

Include:

  1. Brief Introduction
  2. Visual schematic of the experiment
  3. Plot of your data
  4. Comparison to theoretical prediction
  5. Links to your data online
  6. Links to your analysis code online
  7. References in proper format for any external sources you used.