What has to be different to allow refraction to occur?
a. the medium
b. the light
c. the wave
d. the speed

Arunner is training for an upcoming marathon by running around a 100-m-diameter circular track at constant speed. let a coordinate system have its origin at the center of the circle with the x-axis pointing east and the y-axis north. the runner starts at (x, y) = (50 m, 0 m) and runs 2.5 times around the track in a clockwise direction.

Ain is , is 's of ? 0.62 0.79 1.27 1.50

Debris produced by mining is called