1.

Frequency of sound wave is 600Hz. This wave Incidens perpendicular to open door of width 0.75m. At which angle is the first minima obtained ? (speed of light in air = 330 ms^(-1))

Answer»

`20.8`
`45^(@)`
`47.2^(@)`
`83.6^(@)`

SOLUTION :For `m^(th)` order minima `d sin theta_(m)=m LAMBDA`
`0.75 sin theta_(1)= lambda ....(1)`
But `v=lambda F rArr =(v)/(f)`
`0.75 sin theta_(1)=(v)/(f)`
`:. sin theta_(1)=(v)/(fxx0.75)=(330)/(600x0.75)=0.7333`
`:.sintheta_(1)=0.7333`
`:.theta_(1)=47^(@)=10.~~47.2^(@)`


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