Newton's Rings
Safety Warnings
Warning: Mercury Lamp Operation
Warning: Electrical Connections
Purpose
Projects circular interference fringes formed by the air wedge between a plano-convex lens and a flat glass plate. Students observe that the central spot is dark (due to the phase change on reflection), ring spacing decreases with radius, and different wavelengths produce rings at different radii.
Figure 1:
Newton's rings viewed directly through the apparatus, showing concentric colored interference fringes where the plano-convex lens contacts the flat glass plate.
Figure 2:
Optical bench arrangement showing mercury lamp, projection lens, and interference box. The meter stick indicates component spacing for setup.
Figure 3:
Newton's rings apparatus mounted in the soap film interference box, with the projection lens in front and mercury lamp above. The frame rotates to optimize reflected light through the projection lens.
Figure 4:
Enlarged view of Newton's rings showing colored interference fringes. Different mercury wavelengths produce rings at different radii.
Demo Apparatus
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