Question

In a YDSE setup, if the wavelength of light beam incident on slit plane is decreased. What will happen to fringe pattern and number of bright fringes visible on the screen?

• A. Fringe pattern will expand and total number of bright fringes appearing on screen will increase.
• B. Fringe pattern will expand and total number of bright fringes appearing on screen will decrease.
• C. Fringe pattern will shrink and total number of bright fringes appearing on screen will decrease.
• D. Fringe pattern will shrink and total number of bright fringes appearing on screen will increase.

Answer 1

The correct option is D Fringe pattern will shrink and total number of bright fringes appearing on screen will increase.

As fringe width in YDSE is directly proportional to the wavelength of light used, fringe width will decrease due to which overall fringe pattern will shrink. As the fringe pattern is obtained only within the central diffraction maxima of each slit on screen, due to reduced fringe width, total number of bright fringes will increase.