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 ......

Options

A. `80^(@)`
B. `64^(@)`
C. `48^(@)`
D. there is no second order diffraction

Answer

D

Explanation

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.