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Q14.6: NCERT Physics - Part 2 WAVES 14.6 Solution: A bat emits ultrasonic sound of frequency 1000 kHz in air. If…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often incorrectly assume the frequency changes when sound crosses a boundary, but the frequency is determined by the source and remains constant ($f_{reflected} = f_{transmitted} = f_{source}$). You must use the speed of the specific medium the wave is traveling in (air for reflection, water for transmission) paired with the unchanged source frequency to calculate the wavelength.

A bat emits ultrasonic sound of frequency 1000 kHz in air. If the sound meets a water surface, what is the wavelength of (a) the reflected sound, (b) the transmitted sound? Speed of sound in air is 340 m s__ and in water 1486 m s__.

Step-by-Step Verified Solution

**Answer:** (a) λr=3.4×10−4 m\lambda_r = 3.4 \times 10^{-4} \text{ m} (b) λt=1.49×10−3 m\lambda_t = 1.49 \times 10^{-3} \text{ m} **Step-by-Step Explanation:** Frequency f=1000f = 1000 kHz =106= 10^6 Hz. (a) Reflected sound travels in air:
λr=vairf=340106=3.4×10−4 m\lambda_r = \frac{v_{air}}{f} = \frac{340}{10^6} = 3.4 \times 10^{-4} \text{ m}
(b) Transmitted sound travels in water:
λt=vwaterf=1486106=1.49×10−3 m\lambda_t = \frac{v_{water}}{f} = \frac{1486}{10^6} = 1.49 \times 10^{-3} \text{ m}
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All Questions in this Chapter

Q14.1 Q14.2 Q14.3 Q14.4 Q14.5 Q14.6 Q14.7 Q14.8 Q14.9 Q14.10 Q14.11 Q14.12 Q14.13 Q14.14 Q14.15 Q14.16 Q14.17 Q14.18 Q14.19

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