Physics Lab Equipment

LEAI-52 Apparatus for Determining Planck's Constant - Advanced Model

LEAI-52 Apparatus for Determining Planck's Constant - Advanced Model


  • Manual or auto measurement modes

  • Integrated structure and easy to operate

  • No crosstalk between spectral lines

  • Built-in data acquisition card with software for PC use via USB port


This LEAI-52 experimental apparatus for determining Planck's constant is used to demonstrate the photoelectric effect, measure the characteristic curve of a photoelectric tube, verify the existence of "red limit" frequency, and calculate Planck’s constant according to the Einstein’s equation of photoelectric effect. By employing a precision photocell, Planck's constant can be determined with a high accuracy of 3%, either by processing data manually recorded from the apparatus; or by using a built-in data acquisition card to automatically acquire data to a PC via USB port and process the acquired data with software. It is an ideal teaching apparatus for physics laboratories at colleges and universities.

The instruction manual contains comprehensive materials including experimental configurations, principles and step-by-step instructions. Please click Experiment Theory and Contents to find more information about this apparatus.


Wavelength of filters365 nm, 405 nm, 436 nm, 546 nm, 577 nm
Size of apertures2 mm, 4 mm, 8 mm, 10 mm, 12 mm 
Light source50 W Mercury lamp


Wavelength range: 340 ~ 700 nm
Cathode sensitivity: ≥1 µA (-2 V ≤ UKA ≤ 0 V)
Anode dark current: ≤5×10-12 A (-2 V ≤ UKA ≤ 0 V)
Current range10-7 ~ 10-13 A, 3-1/2 digit display
Voltage rangeI: -2 ~ +2 V; II: -2 ~ +20 V, 3-1/2 digit display, stability ≤0.1 %
Zero drift< ±0.2% of full scale (for scale 10-13 A) within 30 minutes after warm-up
Measurement methodZero current method and compensation method
Measurement error3%

Parts List

Main Unit1
Electric Control Unit1
Special BNC Cable2
USB Cable1
Software CD1
Power Cord1
Instructional Manual1

    Apparatus for Determining Planck's Constant.png

V-I curves of different light frequencies

(Click figure to enlarge)

     Apparatus for Determining Planck's Constant.png

Cutoff voltage vs light frequency

(Click figure to enlarge)

       LEAI-52 Software.jpg

User interface panel of software

(Click photo to enlarge)

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