With the laser, the diffracted images on the wall and the light source were on opposite sides of the grating. however, for the hydrogen and sodium lights, the light sources and the diffracted images were on the same side of the grating. do you see any contradiction?

Two students, each riding bicycles, start from the same apartment building and ride to the same building on campus, but each takes a different route. the first student rides 1100 m due east and then turns due north and travels another 1430 m before arriving at the destination. the second student heads due north for 1930 m and then turns and heads directly toward the destination. at the turning point, how far is the second student from the destination?