Simply, the change in FREQUENCY when some noise is moving towards us or away from us. This process is known as the Doppler Effect.
In this concept, we everytime confuse whether we have to add velocities or subtract them.
But this is simple to understand by a minor concept of numerator and denominator.
As like when we have to increase the value, we either add value to numerator or subtract value from denominator. In both cases, the overall value will increase.
Similarly, for decreasing the overall value we either subtract from numerator or add in denominator.
The same case is for velocities, when the noise is coming which implies the sound increases means add velocity to numerator and subtract velocity from denominator.
And, when noise is moving away which implies sound decreases means subtract velocity from numerator and add velocity in denominator.
Hence, this is the candid concept of Doppler Effect which makes it easier to understand.
Learning is worship.... just feel in this way 
Hey Physics, just wanted to say I really enjoy reading your posts. They remind me of someone I used to know that was very special to me. Thank you! 😉
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Thanks for the motivation and thats my pleasure 😄……….
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Reminded me of physics classes.. This concept is interesting
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Thank you 😄
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Very interesting blog! Educational and entertaining.
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Thank you 😊
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You are welcome! I look forward to future posts. Very interesting.
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You’re excellent at making things clear and easy! Thank you!
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Thanks😊
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You are like my physics teacher 😉
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My pleasure 😆
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😊😊
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If one can explain in simple words, one has understood 👍🏻🙏🏻🙏🏻🙏🏻
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Thank you😄
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Good job explaining Doppler Effect!
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Thanks 😊
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