Newton’s Rings Apparatus

Item Code: SK008

Working and Principle :

A plano-convex lens is placed with its convex surface on the optically plane glass plate so as to enclose a thin film of air of varying thickness between the lens and the plate. Light from an extended monochromatic source is converted into a parallel beam of light by using planoconvex lens of large radius of curvature and made to fall on an optically plane glass plate inclined at an angle of 45° to the vertical, where it gets reflected on to the Plano-convex lens. The wavelength of monochromatic light source is determined from the radii of the interference rings.




  • Stand alone setup (built in sodium bulb, microscope,HID blast transformer & optics in a single compact body.
  • Reflector mounted at 45°(no special adjustment required).
  • High quality glass plates (flatness λ/10).
  • Heavy rigid body weight 12.6 Kg approx.
  • Smooth X & Y movement of reflector assembly.
  • Modern compact design required less space in Laboratory.
  • Modern user friendly design.

  • To determine the wavelength of sodium light.
  • To determine the refractive index of a liquid by using Newton’s rings apparatus.
  • To find the radius of curvature of planoconvex lens using spherometer.
  • To find the thickness of a thin sheet of paper (air wedge experiment).
  • Linear motion : 10 – 0 -10mm
  • Micrometer : Vernier dial 100 div., LC 0.01mm
  • Eyepiece : Ramsden 10X
  • Objective : 3X
  • Spherometer disk(brass) : Types 3 legs, Vertical scale 6 x 6mm(WxT) Micrometer dia. 40mm, Brass lower disc dia. 60mm, Range 10-0-10mm, Least count 0.01mm
  • Plano convex lens : Dia. 61.5mm, Glass, Focal length 200mm
  • Sodium source : MS housing, 200 x 85mm (LxØ), slit(LxW) 20x16mm
  • Sodium bulb : 35W
  • Fuse : 2A
  • Body : Al casting
  • Weight : 12.6 kg approx
  • 1 Newton’s ring apparatus
  • 1 Spherometer
  • 1 Plano convex lens with plane glass plate
  • 1 Plain glass plate pair (50 x 35 x 2mm)
  • 1 Plain glass (108 x 70 x 1.2mm)
  • 1 Power cord
  • 1 Plain glass (75 x 75 x 2mm)
  • 1 Sodium bulb
  • Phase relationship
  • Coherent light
  • Path difference
  • Interference.
  • Newton’s rings.
  • Refractive index.
  • Thickness of sheet wavelength.
  • Radius of curvature.