In Young's double slit experiment, the wavelength of red light is 7800 Å and that of blue light is 5200 Å. The value of n for which nth bright band due to red light coincides with (n + 1)th bright band due to blue light, is:
Options

Question

In Young's double slit experiment, the wavelength of red light is 7800 Å and that of blue light is 5200 Å. The value of n for which nth bright band due to red light coincides with (n + 1)th bright band due to blue light, is:

Options

G1 Physics · Accepted Answer

Coincident bright fringes satisfy n(red wavelength)=(n+1)(blue wavelength). Thus 7800n=5200(n+1), giving n=2. Option B.