Physics Lab Equipment

LEOK-70 Balmer Series of Hydrogen & Rydberg Constant

LEOK-70 Balmer Series of Hydrogen & Rydberg Constant


  • Stable aluminum rail for easy alignment

  • Hydrogen-Deuterium lamp

  • Detailed instructional manual


The Balmer series is referred to as a set of discrete emission spectral lines of the Hydrogen atom. The visible Balmer series involves the electron transitions from the higher energy levels (≥ 3) to the second energy level (n = 2) where n is the principal quantum number of the electron.


The wavelengths of the Balmer series of the Hydrogen atom can be calculated from equation 1/λ = R (1/22-1/n2), n=3, 4, 5, ..., where R is an empirical constant called the Rydberg constant (R=1.096776x107 m-1).


This apparatus uses a diffraction grating to disperse the collimated beam of a Hydrogen-Deuterium lamp and a digital protractor stage along with a telescope to measure the diffraction angles of the Balmer series lines. Once the wavelengths are determined, the experimental value of the Rydberg constant can be derived.


Hydrogen-Deuterium LampWavelengths: 410, 434, 486, 656 nm
Digital ProtractorResolution: 0.1°
Condensing Lensf = 50 mm
Collimating Lensf = 100 mm
Transmissive Grating600 lines/mm
TelescopeMagnification: 8 x; diameter of objective lens: 21 mm with internal reference line
Optical RailLength: 74 cm; aluminum

Part List

Optical rail1
X-translation carrier1
Optical rotation stage with digital protractor1
Lens holder2
Adjustable slit1
Telescope holder (tilt adjustable)1
Hydrogen-Deuterium lamp with power supply1 set

LEOK-70 Balmer Series-1.jpg

Spectral lines of Hydrogen atom


LEOK-70 Balmer Series-2.jpg

Schematic of spectral dispersion

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