STEM与日常科技·英语30篇（3）

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多普勒效应与雷达测速

When a police radar gun sends out radio waves, moving cars reflect them back at slightly changed frequencies.
If the car approaches, reflected waves bunch up—raising frequency like a siren pitch rising as an ambulance nears you.
If the car moves away, waves stretch out—lowering frequency, just as the siren drops in pitch after passing.
The radar unit measures this tiny frequency shift—often less than 0.001%—to compute exact speed in miles per hour.
This same principle helps meteorologists track storm rotation and doctors monitor blood flow in arteries.
Unlike lidar, radar works in rain or fog because radio waves penetrate moisture better than laser light.
Speed cameras combine Doppler radar with image capture—timing the shift ensures fairness, not just visual guesswork.
Every time you hear a train whistle change tone, you’re experiencing the same physics that keeps roads safer today.

听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。

This same principle helps meteorologists track storm rotation and doctors monitor blood flow in arteries. 同一原理也被气象学家用于追踪风暴旋转，被医生用于监测动脉血流。
Speed cameras combine Doppler radar with image capture—timing the shift ensures fairness, not just visual guesswork. 测速摄像头将多普勒雷达与图像捕捉结合——通过精确计时频率偏移，确保公平性，而非仅凭肉眼估测。
When a police radar gun sends out radio waves, moving cars reflect them back at slightly changed frequencies. 警用雷达枪发射无线电波，行驶中的车辆会将其反射回来，频率略有变化。

这篇中文题目最接近哪一句？多普勒效应与雷达测速一次学校运动会的通知一份超市购物清单

课文第一句的意思更接近？警用雷达枪发射无线电波，行驶中的车辆会将其反射回来，频率略有变化。今天学校放假了。请把窗户打开。

这一课主要在讲什么？（看英文标题） Doppler Effect and Radar Speed Detection How to cook noodles A maths worksheet

This same principle helps meteorologists track storm rotation and doctors monitor blood flow in arteries.

This same principle helps meteorologists track storm rotation and doctors monitor blood flow in arteries.

第一版：录下来、回听、再听标准音。系统打分以后再加。

用今天的表达，自己说一句。

例子：This same principle helps meteorologists track storm rotation and doctors monitor blood flow in arteries.