Answer:Simple Covalent substance
Explanation:Simple covalent substance describes a substance that has a low melting point and poor electrical conductivity because:
(1)melting point :For the covalent bond and intermolecular force that are present in a simple covalent substance,energy is needed to break the forces of attraction present. In the simple covalent substance, little energy is needed because the intermolecular forces present are broken because they are weaker compared to the covalent bond present.
Therefore, when simple covalent substance melts,only the intermolecular forces are broken leaving only the covalent bond in the substance.
(2) poor conductivity: for a substance to conduct electricity,it must have charged particles which are free to move to and fro.
But in the simple covalent substance,there are no charged particles that can be separated due to the covalent bond present in simple covalent substance.
Answer:
The amplitude is
Explanation:
From the question we are told that
The frequency of when sound is approaching observer is 
The frequency as the move away from observer is 
The time between the pitch are 
Here you are the observer and your friends are the source of the sound
The period is mathematically evaluated as

as it is the time to complete one oscillation which from on highest pitch to the next highest pitch
Now T can also be mathematically represented as

Where
is the angular velocity
=> 
=> 
Now using Doppler Effect,
The source of the sound is approaching the observer
The


Where A is the amplitude
So when the source is moving away from the observer
Here
is the fundamental frequency
Dividing the both equation we have




=> 

The part that moves are called anti-nodes. The stationary pars are nodes
Their 'degrees' are the same size. The difference between the Celsius
and Kelvin scales is their zero-point. Zero Kelvin is the absolute zero of
nature and Physics. Zero Celsius is the melting/freezing point of water,
273.15 higher than absolute zero.