In a large room , a person receives waves from the same source which reach , being reflected from the `25 m` high ceiling at a point halfway between them . The two waves interfere constructively for a wavelength of

Explanation

`S`: source, `O`: Observer
Path difference `Delta x = SAO - SO`
`= 2 SA - SO`
`= sqrt((60)^(2) + (25)^(2)) - 120`
`= 2 xx 65 - 120 = 10 m`
For constructive interference
`Delta x = n lambda rArr 10 = n lambda`
`lambda = (10)/(n) m, n = 1,2,3....`
`lambda = 10 m, (10)/(2) m, (10)/(3) m,...`