Balmer Series And Rydberg Constant

Item Code: SK043

Principle and Working:

Hydrogen atoms in a discharge lamp emit a series of lines in the visible part of the spectrum. This series is called the Balmer series which continues into the ultraviolet range. Rydberg generalized the Balmer’s formula in terms of wave numbers to describe wavelengths of spectral lines of many chemical elements. For hydrogen the Balmer’s formula becomes a special case of Rydberg’s formula and is given by
... 1/λ=R(1/22 _ 1/n2)
where n are integers, 3, 4, 5, … up to infinity and
R is Rydberg constant ( R = 4/B where B is the Balmer’s constant).
In the present setup, the spectral lines of hydrogen is observed by means of diffraction grating. The wavelength of the visible lines of Balmer series of hydrogen are measured by spectrometry.




  • Hydrogen atom filled spectrum tube (USA make).
  • High Voltage spectrum tube (5kV) with safety door and thermal switch.
  • Four Vernier used to remove eccentric error (almost fully)
  • Least count 20 sec. for precise measurement
  • Highly stable spectrometer body (weight 8.5 kg approx.)

  • To determine the wavelengths of Balmer series in the visible region from hydrogen emission.
  • To determine the Rydberg constant.

  • Spectroscope : Observation tube moveable, with locking screw, slidable eyepiece, Objective 18 mm / 160 mm, Symmetrical slit Slit tube, Objective 18 mm / 160 mm, Stationary Scale tube, 200-division scale, Eyepiece 18mm aperture, 90 mm Fl, Prism Flint glass (60°), Dispersion C-F 2°, Height 25 cm (approx.)
  • Spectrum Tube power supply : Input 220V, 50 Hz AC, Output 0-5000 V, Overload 2mA (Max.) Spring loaded socket
  • Spectrum Tube : Hydrogen Gas, Violet 420, 440nm, Blue 490nm, Red 670nm
  • Diffraction Grating : Size 89 x 38 mm, Aperture 16 x 9 mm Rulings 100,300,600 lines/mm
  • 1 Spectrometer (L.C. = 20 sec)
  • 1 Diffraction grating
  • 1 Spectrum tube power supply
  • 1 Hydrogen tube
  • 1 Allen key
  • 1 Magnifier
  • 1 Prism EDF
  • Bohr atomic model.
  • Visible spectrum.
  • Energy level.
  • Diffraction.
  • Rydberg atom.
  • Rydberg’s constant.