When the traffic lights turn red, we will stop driving a car or crossing a street. Why is red used for traffic lights instead of other colors?
As we know, scattering(散射) happens when light goes through the air. For the same media(媒质), if the wavelength islong, the scattering will be short. If the wavelength is short, then the scattering will be long.
Of all lights we can see red has the longest wavelength, so the scattering is the weakest. That means the red light travels far. In fact, it travels farther on rainy days.
Using the red light can help drivers in farther areas sec the lights. It helps drivers stow down or stop in lime. If drivers don't see the red light until they are close, they may not be able to stop the car in time. An accident may happen Red can also excite people. We can act more quickly when we see the color red. In a word, red lights help drivers stop in time and help prevent accidents.
When the traffic lights turn ______, we will stop driving a car.
A. red    B green     C. yellow
According to the passage, the scattering of the red light is the _______.
A. longest    b. weakest       C. farthest
The underlined word "wavelength" means________ in Chinese.
A.波浪        B.光波      C.波长
What can the red light help drivers do?
A. It can help drivers in farther areas see the lights.
b. It can help drivers slow down or stop in time.
C.A and b
Which of the following is the best title?
A. Why do accidents happen
b. How does the red light travel
C. Why do we use red traffic lights