A beam of white light passes through a glass prism and forms a spectrum on a screen. If you place a second identical prism after the first, inverted with respect to it, what will happen to the spectrum?
The spectrum will recombine into white light
A glass prism splits white light into its seven colours (VIBGYOR) because each colour has a different refractive index in glass and so bends by a different amount; violet bends the most and red the least. This splitting is called dispersion.
When a second identical prism is placed inverted with respect to the first, it bends each colour by the same amount but in the opposite direction. So the deviation and the dispersion produced by the first prism are cancelled by the second.
Therefore all the colours emerge travelling together, parallel to the original beam, and the spectrum recombines into white light on the screen. Newton used exactly this arrangement to show that white light is made up of these seven colours.
Because the second prism undoes the splitting, the colours do not spread further apart, do not stay separated in reverse order, and no second spectrum is formed.
Hence, The spectrum will recombine into white light.
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Important Questions from Optics
Who was the first one to use a glass prism to obtain the spectrum of sunlight?
Twinkling of stars is due to:
In which a convex mirror is used?
A. Rear View mirrors in vehicles
B. Glass windows
C. Makeup Mirror
D. Kaleidoscope
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The power of a lens is -2.5 D. The type of lens and its focal length are respectively:
