A bat emitting an ultrasonic wave of frequency 4.5 x 10' Hz at speed of 6 m/s between two parallel walls. The two frequencies heared by the bat will be

4.67 x 10⁴ Hz, 4.34 x 10⁴ Hz

4.34 x 10⁴ Hz, 4.67 x 10⁴ Hz

4.5 x 10⁴ Hz, 5.4 x 10⁴ Hz

4.67 x 10³ Hz, 4.34 x 10⁴ Hz

Solution

4.34 x 10⁴ Hz, 4.67 x 10⁴ Hz

4.67 x 10³ Hz, 4.34 x 10⁴ Hz

Frequency received by bat after reflection from wall (1),

f₁ = f $[\frac{v + u}{v - u}]$

= 4.5 × 10⁴ $[\frac{330 + 6}{330 - 6}]$

[ given f = 4.5 × 10⁴ Hz ]

= 4.67 × 10⁴ Hz

Frequency received by bat after reflection from wall (2),

f₂ = f $[\frac{v - u}{v + u}]$

= 4.5 × 10⁴ $[\frac{330 - 6}{330 + 6}]$

f₂ = 4.34 × 10⁴ Hz

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