1.

Light is incident normally on a diffracting grating through which the first diffraction is seen at 32^(@). In this case the second ordei diffraction will be ......

Answer»

`80^(@)`
`64^(@)`
`48^(@)`
there is no second ORDER DIFFRACTION

Solution :In Fraunhoffer diffraction by single slit,
`d sin theta_(n)=n lambda`
for first order minimum
`:.d sin 32^(@)=1 xx lambda rArr lambda= d sin 32^(@)`
Now, for second order minimum
`d sin theta_(2)= 2xx lambda`
`:. D sin theta_(2)=2xx d sin 32^(@)`
`:. sin theta_(2)=2xx sin 32^(@)`
`=2xx0.529`
`sin theta_(2)=1.06`
but the value of sin NEVER be GREATER than 1 so second order minimum cannot OCCUR.


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