Physics Q101 – AP-EAMCET 2025

If a sound wave emitted by a stationary source of frequency

680 Hz

travels towards a stationary observer

150 m

away, then the number of waves between the source and observer are (speed of sound in air

= 340 {m s}^{- 1}

)

Clue 1 of 3: Wave Properties

Understand the fundamental relationship between the speed, frequency, and wavelength of a wave.

🧠 Full Solution Path

Step 1: Identify Given Parameters✦ Active

The problem provides the frequency of the sound wave, the distance between the source and observer, and the speed of sound in air. We need to find the number of waves present in the given distance.

f = 680 Hz

D = 150 m

v = 340 {m s}^{- 1}

💡 Teacher's Secret Hint

Ensure all units are consistent (e.g., meters, seconds, Hertz) before performing calculations.

Step 2: Calculate Wavelength○ Expand

The relationship between the speed of a wave ( $v$ ), its frequency ( $f$ ), and its wavelength ( $λ$ ) is given by the formula $v = f λ$ . We can rearrange this to find the wavelength.

λ = \frac{v}{f}

λ = \frac{340 {m s}^{- 1}}{680 Hz}

λ = 0.5 m

💡 Teacher's Secret Hint

Remember that $1 Hz = 1 s^{- 1}$ , so the units cancel out correctly to give meters for wavelength.

Step 3: Determine Number of Waves○ Expand

The total number of waves ( $N$ ) present in a given distance ( $D$ ) is simply the total distance divided by the length of a single wave (wavelength $λ$ ).

N = \frac{D}{λ}

N = \frac{150 m}{0.5 m}

N = 300

💡 Teacher's Secret Hint

This calculation essentially tells you how many "cycles" of the wave fit into the specified distance.

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Physics Question 101 – AP-EAMCET 2025

Clue 1 of 3: Wave Properties

🧠 Full Solution Path