________________ refers to the superposing of two or more coherent waves to produce regions of maxima and minima in space, according to the principle of superposition.
A boat is sailing towards a lighthouse of height 20√3 m at a certain speed. The angle of elevation of the top of the lighthouse changes from 30° to 60° in 10 seconds. What is the time taken (in seconds) by the boat to reach the lighthouse from its initial position?