In a Young's double slit experiment, slits are separated by 0 . 5 mm , and the screen is placed 150 cm away. A beam of light consisting of two wavelengths, 650 nm and 520 nm , is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is:

Step-by-step solution

Given, Wavelength of first light is, λ 1 = 650   nm Wavelength of second light is, λ 2 = 520   nm Screen distance is, D = 150   cm Slit width is, d = 0 . 5   mm For first wavelength, location of fringe from central line, y 1 = n 1 λ 1 D d for bright fringes For second wavelength, location of fringe from central line, y 2 = n 2 λ 2 D d for bright fringes Condition of coincide of fringe is, y 1 = y 2 ⇒ n 1 λ 1 = n 2 λ 2 ⇒ n 1 × 650 = n 2 × 520 &#