The volcanoes and the safety precautions must be taken at the occurrence of the volcanoes .

Lava ( lava flows ) are molten materials mass that spreads on the volcanic sides .

There are thousands of volcanoes on the Earth's surface . But sixty one only of them are active as an evidence of the permanent activities and movement beneath the Earth's crust . 

Earthquakes and safety precautions must be taken at the occurrence of earthquakes

Earthquakes are rapid and successive shakes of the ground which take place one after the other . 

 

Every day , the Earth's crust is exposed to nearly 400 earthquakes . actually we do not feel them , but the seismic and remote sensation detecting centers record and track them .

Mechanical waves and some technological applications of sound mechanical waves

 

Do you know that Mechanical waves  are waves which propagate through a material medium ( solid , liquid , or gas ) at a wave speed which depends on the  properties of that medium ?

 

Examples and some technological applications of electromagnetic waves

 

Light , microwaves , x - rays , TV and radio transmissions are all kinds of electromagnetic waves .

Electromagnetic waves are formed when an electric field couples with a magnetic field . The magnetic and electric fields of an electromagnetic waves are perpendicular to each other and to the direction of the wave .

 

The lunar eclipse and safety precautions on observing the lunar eclipse

 

Do you know that The lunar eclipse occurs when the Sun , Earth and the Moon are nearly on one straight line with the Earth in the middle hiding the sunlight from the Moon  ?

 

Do you know that the lunar eclipse occurs in the middle of the lunar month ( the moon phase is full moon )  at a rate of two lunar eclipses per year ? .

 

The types of the solar eclipses and safety precautions on observing the solar eclipse

 

The solar eclipse phenomenon occurs when the Moon passes between the Sun and the Earth casting its shadow on the Earth's surface , where the moon ,the Earth and the Sun are nearly on one straight line with the moon in the middle . 

 

The solar system and the milky way galaxy

The galaxy that our solar system belongs to is known  as " The way of chopped hay galaxy " or " The Milky Way galaxy " It takes an oval shape with coiled spiral arms extend from it , the Sun lies on one of these spiral arms . The solar system consists of the Sun , the Planets , the Moons , the Asteroids , the Meteors , the Meteorites and the Comets .

 

Benefits and dangers of electricity

 

You should know that electricity is very important in our life . Everyone needs electricity . We can not imagine our life without it , So it also has benefits and dangers . We must know how to deal with it .