Uses Of Periscope
It is used in submarines to determine the distance of a torpedo and helps in deciding the right time for the attack.
It is used in a nuclear reactor to observe the chemical reactions that are taking place.
In military periscopes are used to observe from their hiding position. Hi
The vertical columns on the periodic table are called groups or families because of their similar chemical behavior. All the members of a family of elements have the same number of valence electrons and similar chemical properties. The horizontal rows on the periodic table are called periods.
Properties change within a Row (or period) as the number of valence electrons in the outer shell increase
Answer is number 4.
The above diagram shows a part of our solar system.The planet which is very close to the sun is Mercury. Hence, No.1 is Mercury and 2 and 3 are Venus and Earth respectively. Moon is an astronomical body which orbit planet Earth. Hence moon should be shown near to the planet Earth.