Question

: Interference is not observed if the two coherent slit sources are broad. : A broad source is equivalent to many narrow slit sources.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (A)

If both assertion and reason are true and reason is the correct explanation of assertion

Answer 2

Coherent light from two narrow parallel slits will produce an interference pattern on a screen. A broad source is equivalent to a large number of parallel narrow slits, lying side by side. As there are many slits, there will be many overlapping interference patterns may be formed. The overlapping will be to such an extent that all traces of a fringe system will be lost. Thus almost even illumination will be observed. There will be no interference pattern seen. Thus for obtaining a distinct interference fringe pattern, a narrow slit is required.