This is called rectification, and rectifier diodes are most commonly used in low current power supplies. A switching diode is most often used to turn a circuit on or off, and band switching diodes are used for switching high frequency band signals.
Thunder occurs when energy from lightning heats and rapidly expands the air. The resulting sound wave gets heard as thunder. While lightning and thunder occur at roughly the same time, lightning travels at the speed of light, or at 186,000 miles a second, while thunder travels at the speed of sound, equivalent to one-fifth of a mile in one second. People see the lightning long before they hear the thunder.
Thunderstorms happen when two air masses (hot air and cold air) collide. As it gets later in the day the sun in not at an angle where the it is heating up the air as much thus creating cooler air. When the cooler air hits the warmer air the chance of a thunderstorm occurs.