Laser light of wavelength 630 nm incident on a pair of slits produces an interference pattern in which the bright fringes are separated by 8.1 mm. a second light produces an interference pattern in which the fringes are separated by 7.2 mm. calculated the wavelength of the second light.

Explanation

From relation `beta=(lamdaD)/(d)`, we find that, other factors remaining unchanged `(beta.)/(beta)=(lamda.)/(lamda)`
In present problem `beta=8.1`mm, `beta.=7.2mm and lamda=630mm`
`therefore lamda.=(beta.)/(beta)*lamda=(7.2mm)/(8.1mm)xx630nm=560nm`