Consider the following statements: 1. The loudness of a sound is determined basically by its frequency. 2. The frequency of the sound wave does not change when it travels from one medium to another. 3. Audible range of the average human ear extends from about 20 Hz to 20 kHz. How many of the statements given above are correct?

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Correct Answer

B Only two

The loudness of a sound is determined by its amplitude and is proportional to the square of the amplitude, whereas the frequency determines the pitch or shrillness of the sound. Hence, statement 1 is incorrect.
When a sound wave passes from one medium to another, its speed and wavelength change but its frequency remains the same, because frequency is determined by the source of the sound. Hence, statement 2 is correct.
The audible range of the human ear is from about 20 Hz to 20,000 Hz, that is 20 kHz. Sound below 20 Hz is called infrasonic and above 20 kHz is called ultrasonic. Hence, statement 3 is correct.
Therefore, only two statements are correct.