5. Two friends are 90-m apart and begin to walk towards one another. One friend walks at a rate of 2 m/s as the other walks at 3 m/s. How long
before the two friends come into contact with one another?
(A) 18 s
(C) 755
(B) 7.55
(D) 450 $

Sawyer is studying diffraction. he draws a diagram of a plane wave to show how light waves travel. which best describes sawyer’s error? the wave fronts should be perpendicular to the direction in which the waves move. the arrow showing the direction of movement of the waves should be pointing to the left. the arrow showing the direction of movement of the waves should be pointing downward. the wave fronts should be both parallel and perpendicular to the direction in which the waves move.

Use 4 to 5 complete sentences, explain the concepts of beats and how beats are produces.

Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space? the cloud is extremely hot. the cloud is visible primarily because it reflects light from nearby stars. the cloud is cool and lies between you and a hot star. the cloud is cool and very dense, so that you cannot see any objects that lie behind it.