It only occurs when there is an electric current
I think so it ans wold be d.because if the source approaches the observer more and more wavefront will pass and it get squeezed.so wavelength decreases and frequency increases.
All Mountains are built through a general process called "deformation" of the crust of the Earth. Deformation is a fancy word which could also mean "folding". An example of this kind of folding comes from the process described below.
<span>When two sections of the Earth's lithosphere collide, rather than being subducted, where one slab of lithosphere is forced down to deeper regions of the Earth, the slabs pile into each other, causing one or both slabs can fold up like an accordion. This process elevates the crust, folds and deforms it heavily, and produces a mountain range. Mountain building and mantle subduction usually go together. </span>
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All waves must ____ have to travel through
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Explanation:
Wave
It is the periodic disturbance in a medium.
Types of Wave
There are two types of wave in general depending upon their propagation through a substance.
• Mechanical
• Electromagnetic
Mechanical Wave
It is the kind of wave which needs medium to travel. For example: Sound Wave
That means sound can be heard only whenever there is presence of certain substance like water, glass, air etc .It can’t be heard in vacuum no matter how loud is the sound.
Electromagnetic Wave
Is that which can travel through medium as well as through vacuum. For example: Light
But unlike sound, light can be seen through a substance or in vacuum. That is the reason it is referred as electromagnetic wave.
