In Young's double slit experiment the slits are 3 mm apart and are illuminated by light of two wavelengths $$3750 \mathop A\limits^o$$ and $$7500 \mathop A\limits^o$$. The screen is placed at 4 m from the slits. The minimum distance from the common central bright fringe on the screen at which the bright fringe of one interference pattern due to one wavelength coincide with the bright fringe of the other is

When monochromatic light of wavelength 600 nm is used in Young's double slit experiment, the fifth order bright fringe is formed at 6 mm from the central bright fringe on the screen. If the experiment is conducted with light of wavelength 400 nm from the central bright fringe, the third order bright fringe will be located at

The position of the direct image obtained at O, when a monochromatic beam of light is passed through a plane transmission grating at normal incidence is shown in figure. The diffracted images A, B, and C correspond to the first, second and third order diffraction. When the source is replaced by another source of shorter wavelength,

In Young’s double slit experiment, the separation between the slits is halved and the distance between the screen is doubled. The fringe width is