Coherent light of wavelength 
is incident normally on a double slit of slit separation 
. A series of bright and dark fringes forms on a screen placed at a distance of 
from the double slit, as shown. The screen is parallel to the double slit.
Determine the distance between the centres of adjacent bright fringes on the screen.
The light of wavelength is replaced with red light of a single frequency. State and explain the change, if any, in the distance between the centres of adjacent bright fringes.
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