Answer: 
Explanation:
Given
The frequency of the source is 
Change in frequency is 
Speed of sound 
Suppose
is the velocity of the observer
Doppler frequency is given by

Here, the source is at rest
While approaching source, frequency is

While leaving, frequency is

The difference in the frequency is

I would love to help; where’s the picture?
. Methylated spirits have ethanol as a base but may include methyl alcohol (methanol) as part of the denaturing process.
B. Barometer is used to measure atmospheric pressure.