PHYSICS 0/N/06 P1 Q27.

[aliya_zad]

27 The interference patterns from a diffraction grating and a double slit are compared.
Using the diffraction grating, yellow light of the first order is seen at 30° to the normal to the
grating.
The same light produces interference fringes on a screen 1.0 m from the double slit. The slit
separation is 500 times greater than the line spacing of the grating.
What is the fringe separation on the screen?

 

[hassam]

we know d sin(A)=n*lambda
A=30 deg....so sinA=0.5.....we get 0.5d=lambda

X=(Lambda*D)/a
substitute 0.5d for lambda and a ll be 500d
u get fringe separation of 10^-3 m.....i.e option C

 

[aliya_zad]

Thank you so much. This really helped.