What Thunder Tells Us
Written by Studio AM.
Your result
- Words per minute
- Score
- Pace
Words per minute mean something only with the score beside them. They describe this passage on this read. With fewer than 3 right, try the next slower pace.
Choose a pace and select Start. The passage is paced and timed, then the questions check what you understood. How pace mode works
Reading time 0:00
Lightning produces both a flash and thunder. You see the flash first because light travels much faster than sound. Sound takes about three seconds to travel one kilometre through air.
The delay gives a rough distance to the lightning. Divide the seconds between the flash and the first rumble by three. A nine-second delay means the lightning was about three kilometres away. This estimate does not tell you whether you are safe: if you hear thunder, seek shelter in a substantial building or a fully enclosed, hard-topped vehicle.
Thunder begins when lightning rapidly heats the air along its narrow channel. The hot air expands and pushes on the air around it. That pressure change travels outward as a sound wave.
Thunder can sound like a sharp crack or a long roll. Sound from different parts of a lightning channel can reach you at different times. Echoes and conditions in the air can also change what you hear.
The passage is hidden while you answer. It comes back with your result.
Questions
Choose an answer. The explanation appears after you answer.
-
Question 1 of 4
What is the main point of the passage?
The answer is C: How thunder forms and why its delay gives a rough distance to lightning.
The passage explains how lightning produces thunder and how sound's slower travel lets us estimate the distance.
-
Question 2 of 4
How far does sound travel in about three seconds, according to the passage?
The answer is A: One kilometre
The first paragraph states that sound needs about three seconds to travel one kilometre.
-
Question 3 of 4
A person counts fifteen seconds between the flash and the crash. What does the passage suggest?
The answer is D: The lightning was about five kilometres away.
The rule given is to divide the seconds by three, so fifteen seconds means roughly five kilometres.
-
Question 4 of 4
In this passage, 'channel' means:
The answer is A: the narrow path the lightning follows through the air
Lightning heats the air along its 'narrow channel'. Here, the channel is the path it follows through the air.
Score: none answered yet.