Physics Lab Equipment

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

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


  • More accurate measurement results by using micro current meter

  • Integrated structure and easy to operate

  • No crosstalk between spectral lines

  • No background current


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%. It is an ideal teaching apparatus for physics laboratories at colleges and universities.


Wavelength of filters365 nm, 405 nm, 436 nm, 546 nm, 577 nm
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 measurement range10-7 ~ 10-13 A, 3-1/2 digit display
Phototube power supplyI: -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
Power Cord1
Instruction Manual1

     Apparatus for Determining Specific Charge of Electron.jpg

Schematic of photoelectric effect

    Apparatus for Determining Planck's Constant.png

V-I curves of different light frequencies

     Apparatus for Determining Planck's Constant.png

Cutoff voltage vs light frequency

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