Check to make sure that your tape recorder is putting out sound. Plug your tape recorder in your sound modulator. Test your system by shining the light on the solar cell. Get together with another lab group to transmit and receive sound. Your communication system uses visible light to transmit a signal through the air.
Most communication systems use radiowaves or microwaves.
The induction coil acts as a short circuit for the direct current from the battery. As a result, when the flashlight is turned on, current flows through the coil and the lamp is lit. The induction coil acts as an open circuit for the alternating current from the tape player. As a result, the electrical pulses that would power the headphones must flow through the flashlight bulb. These fluctuations are picked up by the solar cell and are turned into electrical pulses, which are amplified by the speaker or tape recorder and turned back into sound.