Final answer:
In 1938, Orson Welles dramatized 'The War of the Worlds' on radio, causing panic among listeners and demonstrating the medium's power. Radio was influential, used by President Roosevelt for his 'fireside chats', and was a primary source of news and entertainment in the 1930s.
Step-by-step explanation:
The power of radio as a medium of mass communication was demonstrated in 1938 when Orson Welles put on a dramatization of The War of the Worlds. This event was a milestone in mass media history, where the Mercury Theater of the Air broadcast a performance that simulated radio news reports of an alien invasion. This caused widespread panic among listeners who believed the fictional events to be real, highlighting the influence and reach of radio as a mode of communication.
President Franklin D. Roosevelt also capitalized on radio's potential, using it to broadcast his 'fireside chats' and connecting with the American public in a more personal way. The 1930s marked a significant period where the populace turned to radio for entertainment, news, and political speeches, illustrating the pivotal role it played in shaping public opinion and behavior.