Answer:
That is, mechanical waves cannot travel through a vacuum. This feature of mechanical waves is often demonstrated in a Physics class. A ringing bell is placed in a jar and air inside the jar is evacuated. Once air is removed from the jar, the sound of the ringing bell can no longer be heard.
Answer: Limiting reactant
Explanation:
The limiting reactant is a reactant will get completely consumed up in the reaction. This reactant being in low concentration will lead to the formation of limited amount of product.
In the given situation, since the butter cakes are required to be 3 sticks for making 3 cakes but only 2 cakes are available thus the butter stick is the limiting reactant.
The perceived frequency when the fire truck is moving toward you and away from you will be 370 Hz and 329.59 Hz respectively.
<h3>What is the Doppler effect?</h3>
A sudden change in the frequency due to the distance between the objects and source is explained by the doppler effect.
As the source and observer travel toward each other, the frequency of sound, light, or other waves increases or decreases.
The perceived frequency when the fire truck is moving toward you;

The perceived frequency when the fire truck is moving away from you;

Hence, the perceived frequency when the fire truck in cases 1 and 2 will be 370 Hz and 329.59 Hz.
To learn more about the doppler effect refer to the link;
brainly.com/question/15318474
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Answer:
Concave lenses are used in eyeglasses that correct myopia or nearsightedness.