A laser pointer is placed 20cm in front of a plane mirror on a laboratory table. The laser is directed exactly along the normal to the mirror so that the beam falls perpendicularly on the surface.
(i) Calculate the total distance travelled by the light pulse from the pointer until it returns to its source after reflection.
(ii) Determine the time taken for the pulse to return. \;(Take the speed of light c=3.0×108m s−1.)