An artificial satellite can be tracked very precisely from the earth by using Doppler effect.

The minimum distance from the eye at which an object appears to be distinct is called least distance of distinct vision or near point. It is about 25 cm for human eye.

The radioactivity of uranium was discovered in 1896 by Henri Becquerel.

In the next years, it was found that thorium was radioactive too, and two new radioactive elements, polonium and radium, were discovered by Pierre and Marie Curie.

Pierre and Marie were award the Noble Prize in Physics in 1903 for their work on radioactivity. Marie Curie became the first woman to be awarded the nobel prize and the first person to obtain two nobel prizes when she won the prize for the discovery of Polonium and Radium in 1911.

Though it was Henri Becquerel that discovered radioactivity, it was Marie Curie who coined the term.

Radar is mainly used to detect the direction and range of objects by means of radio waves

Devices and body parts measured by it:

Electrooculography (EOG) – Eyes
Electromyography (EMG) – Muscles
Electrocardiography (ECG) – Heart
Electroencephalography (EEG) – Brain