A physicist is replicating a historic 17th-century demonstration to compare Isaac Newton's corpuscular model of light with Christiaan Huygens' wave model of light.
Initially, the physicist directs a parallel beam of monochromatic blue light at a barrier with two wide, widely spaced slits, as shown in Setup A of the diagram.
The physicist observes two sharp, bright blue rectangular bands on the screen in Setup A, separated by a dark region of shadow. Explain how this observation supports Newton's corpuscular theory of light.
The physicist then modifies the apparatus to obtain the pattern of alternating blue and dark fringes shown in Setup B.
Identify the alterations that must be made to the apparatus in Setup A to observe this pattern, and explain how the observations in Setup B support Huygens' wave theory of light.
In your answer, you should:
- State the physical alterations required to transition from the apparatus in Setup A to Setup B.
- Outline the key principles of Huygens' wave theory of propagation.
- Explain, using Huygens' theory, how the pattern of alternating blue and dark fringes is formed on the screen.