<span>Vibration waves from earth quakes travel through the earth and have measurable speed. And the different temperatures and fluidity of the various regions of the mantle will change that speed and or reflect the vibration waves in different directions. With multiple vibration sensors around the world the time that it takes for vibrations to travel from one part of the world to another will tell you what is inside.</span>
Answer:The Doppler effect is a change in the frequency of sound waves that occurs when the source of the sound waves is moving relative to a stationary listener.
As the source of sound waves approaches a listener, the sound waves get closer together, increasing their frequency and the pitch of the sound. The opposite happens when the source of sound waves moves away from the listener.
Explanation:
Answer:
Explanation:
Assuming uniform spread of sound with no significant reflections or absorption. We know that sound intensity varies 
where r is the distance
Since intensity is given then when at 3 m
Since we have the constant then at 4m
Intensity, 
Elements with 7 valence electrons are extremely reactive, while elements with 8 valence electrons practically don't react at all.
This is caused by the fact that all molecules want to have 8 valence electrons; that's just the scientific fact. So, if an element already has 8 valence electrons, it doesn't need to react with anything. If the element only has 7 valence electrons, however, it really wants to react with something with 1 valence electron to get to that special number 8.
Answer:
The correct option is A. 18 V
Therefore,
Explanation:
Given:
Total Voltage,
V = 56 V,
Voltage drop
To Find:
(Assumed ,as it is not given clearly in the question)
Solution:
So in series combination total Voltage is given as
Substituting the values we get
Therefore,
