Question

White light is split into a spectrum by a prism and it is seen on a screen. If we put another identical inverted prism behind it in contact. What will be seen on the screen ?

• A. Violet will appear where red was
• B. The spectrum will remain the same
• C. There will be no spectrum, but only the original light with no deviation.
• D. There will be no spectrum, but the original light will be laterally displaced

Answer 1

The correct option is D There will be no spectrum, but the original light will be laterally displaced

Answer is D.
After the second prism refraction, the light rays emerge parallel to each other just as they were in the incident beam of light, and hence this looks like white light.
Hence, when we put another identical inverted prism behind it in contact, there will be no spectrum, but the original light will be laterally displaced.