Answer:
An opaque object with many closely spaced slits
Step-by-step explanation:
Diffraction grating is an opaque object which will have many close slits on it
Each slit will allow the light wave pass through it which incident on it.
So here each slit will behave like a secondary source which will transmit the light and the superposition of light is then observed on the screen
These large number of slits on the object is combined known as diffraction grating.
By the superposition of waves due to grating we will have pattern of maximum and minimum intensity on the screen and this intensity if highest at the mid point of screen and then decreases as we move away