Rotating difraction grid

[phy_magic]

Homework Statement

A narrow monochromatic laser beam is incident perpendicular to the diffraction grating. How it changes
interference pattern on the screen if the grid rotates by an angle φ<90o
around an axis which is:
a) parallel to the notches (cracks) of the grid
b) perpendicular to the notches (cracks) of the grid

Relevant Equations

If grid lies in xy plane and z axis is out of paper what axis should i choose for rotation? Does iz affect on d in difraction equations. d sina=mλ

I starter with difraction equations dsina=mλ, depending on rotation s d will and then a shoud also change but i still don t know how

 

[Steve4Physics]

Homework Statement: A narrow monochromatic laser beam is incident perpendicular to the diffraction grating. How it changes
interference pattern on the screen if the grid rotates by an angle φ<90o
around an axis which is:
a) parallel to the notches (cracks) of the grid
b) perpendicular to the notches (cracks) of the grid
Relevant Equations: If grid lies in xy plane and z axis is out of paper what axis should i choose for rotation?

With the diffraction grating ('grid') like this:

- to which axis of rotation (x, y or z) do you think part a) refers ?
- to which axis of rotation (x, y or z) do you think part b) refers ?

Does iz affect on d in difraction equations. d sina=mλ

What is 'iz'?

'd' is the distance between adjacent lines in the 'grid'. It can't change.

I starter with difraction equations dsina=mλ, depending on rotation s d will and then a shoud also change but i still don t know how

I recommend you:
1) make sure you fully understand how the image is formed in the simplest case - when the laser is incident perpendicular to the diffraction grating;
2) do a search for 'diffraction grating oblique incidence'.

Minor (cosmetic) edits.