Hi, I'm currently taking a Wave and modern physics class and we recently finished two chapt: interference and diffraction. I'm having a hard time grasping the difference. I understand that diffraction is the expansion of light when it goes through a small opening ( it "flares" out contrarily to geometrical optics). I also understand that interference is when two light waves "meet" and "create a new wave" ( in simple terms I guess). I get stuck at the part where my book says : "when monochromatic light from a distant source (or a laser) passes through a narrow slit and is then intercepted by a viewing screen, the light produces on the screen a diffraction pattern" How can diffraction create a pattern on a screen? We haven't spoken of Hyugen princple in class but I know its due to that. Only that all points on a wavefront serve as point source of spherical secondary wavelet. Really I don't understand how that helps me with diffraction :/ I'm sorry this may sound really dumb and confusing but I hate solving problems without understanding what I am doing Thank you for anybody who take time to answer and I'm sorry if this is in the wrong section.