What is the main point of the passage?

The gap between the flash and the crash has a simple cause, and it can be used to measure distance. (The passage explains why the sound arrives late, turns that delay into a distance, and then explains what makes the sound.)

How far does sound travel in about three seconds, according to the passage?

One kilometre (The first paragraph states that sound needs about three seconds to travel one kilometre.)

A person counts fifteen seconds between the flash and the crash. What does the passage suggest?

The strike was about five kilometres away. (The rule given is to divide the seconds by three, so fifteen seconds means roughly five kilometres.)

In this passage, 'channel' means:

the narrow path the lightning follows through the air (The text says lightning heats 'the narrow channel it passes through', so the channel is the thin path of the strike.)

Counting Toward Thunder: Level 2 Reading Comprehension Questions

A flash of lightning and the crash of thunder begin at the same moment. You see the flash first because light travels much faster than sound. Light crosses the sky almost at once. Sound needs about three seconds to travel one kilometre.

So you can turn the delay into a measurement. Count the seconds between the flash and the first rumble, then divide by three. The answer is the rough distance to the strike in kilometres. Nine seconds means the lightning was about three kilometres away.

Thunder itself is made of air. Lightning heats the narrow channel it passes through to a temperature far hotter than the surface of the sun. The air in that channel expands in an instant and pushes hard on the air around it. That push spreads outward as a wave, and your ear hears a crash.

Near strikes sound sharp and short. Distant ones sound like a long roll, because the sound reaches you from different parts of the same long channel at slightly different times.

Comprehension questions