In which step(s) did a chemical change most likely occur?

One day, after pulling down your window shade, you notice that sunlight is passing through a pinhole in the shade and making a small patch of light on the far wall. you see that the patch of light seems to be a circular diffraction pattern. it appears that the central maximum is about 1 cm across and you estimate that the distance from the window shade to the wall is about 3 m. what is (a) the average wavelength of sunlight? (b) the diameter of the pinhole?

Idon’t quite understand this problem

Need asap ‼️ 20 pts which gravitational force field diagram is drawn correctly? (answers in pictures below)