Question 1

Two identical waves (having the same wavelength and amplitude) interfere with each other. The initial amplitude of each wave was 28 cm; the resultant wave has an amplitude of 12 cm. What is the phase difference between the waves represented as a fraction of a wavelength?

Accepted Answer

The answer of Two identical waves (having the same wavelength...

Question 2

Which note is represented by the wave equation y(x, t) = 2sin[(1642 s^-1)t - (4.79 m^-1)x? For reference, use Table 14.1.

Accepted Answer

The answer of Which note is represented by the wave...

Question 3

A reflected wave on a fixed end is inverted, but does not change shape. A reflected wave on a loose end is not inverted, nor does it change shape.

Accepted Answer

When a wave reflects off a fixed end, it inverts due to the boundary condition that the displacement must be zero at the fixed end. However, the shape of the wave does not change, only its direction. On a loose end, the wave reflects without inversion because the boundary allows for maximum displacement, but like with the fixed end, the shape of the wave remains the same.

Question 4

Figure 14.5 Fig. 14.5 shows a sound wave. -Fig. 14.5 shows a sound wave in the air. L₁ = 200 ìPa, L₂ = 52.4 cm. Which note from Table 14.1 is represented? What is the amplitude of the wave? Take the speed of sound in the air as 343 m/s.

Accepted Answer

The answer of Figure 14.5
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Fig. 14.5 shows a...

Question 5

For waves moving at a given speed, the frequency is higher if the wavelength is smaller.

Accepted Answer

The speed of a wave is equal to the product of its frequency and wavelength. Therefore, if the speed is constant and the wavelength decreases, the frequency must increase to maintain the same speed.

Question 6

The length of a string contains an integer number of halves of wavelengths of harmonics.

Accepted Answer

The length of a string supports integer multiples of half wavelengths for its harmonics, meaning each harmonic frequency produces a standing wave that fits exactly into the length of the string in whole or half wavelengths.

Question 7

The frequency of a wave is determined by the source of the wave, but wavelength is not. Wavelength depends on the medium through which the wave propagates.

Accepted Answer

The frequency of a wave is indeed determined by its source and remains constant when the wave moves from one medium to another. However, the wavelength can change when the wave enters a different medium because the speed of the wave changes, while the frequency remains the same.

Question 8

The wave described by the equation y(x, t) = (4 cm)sin[(0.5 cm)x + (1.05 s^-1)t)] is moving along the x-axis in the positive direction (to the right).

Accepted Answer

The wave equation y(x, t) = (4 cm)sin[(0.5 cm)x + (1.05 s⁻¹)t)] has a positive sign in front of the time variable term, indicating that the wave is moving in the negative x-direction (to the left).

Question 9

When a wave passes through a certain medium, the particles of the medium move with the wave. For example, a sound wave propagates through air via air molecules that move from the source to receiver.

Accepted Answer

When a wave passes through a medium, the particles of the medium oscillate around their equilibrium positions, but they do not travel with the wave. The wave transfers energy, not particles, from one place to another.

Question 10

Bats use ultrasound to locate prey. The wavelength of sound has to be of the order of size of the prey if the prey is to be detected. What is the size of the smallest insect a bat can detect if it emits a sound at 55 kHz? The speed of sound is 343 m/s.

Accepted Answer

The answer of Bats use ultrasound to locate prey. The...

Question 11

Constructive interference occurs only when two harmonious waves arrive at the same point with a phase difference of exactly 1 wavelength.

Accepted Answer

Constructive interference occurs when two waves meet in phase (with a phase difference of 0, or an integer multiple of 2π radians, which corresponds to an integer number of wavelengths), not necessarily exactly 1 wavelength apart.

Question 12

Figure 14.6  Fig. 14.6 shows a sound wave.
-What is the amplitude of the wave represented in Fig. 14.6? What are the wavelength and the frequency, assuming that it is a sound wave in air? The speed of sound in air is 343 m/s.

Accepted Answer

The answer of Figure 14.6  Fig. 14.6 shows a...

Question 13

Figure 14.5 Fig. 14.5 shows a sound wave. -Fig. 14.5 shows a sound wave in the water. L₁ = 220 ìPa, L₂ = 226 cm. Which note from Table 14.1 is represented? What is the amplitude of the wave? Take the speed of sound in the water as 1482 m/s.

Accepted Answer

The answer of Figure 14.5
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Fig. 14.5 shows a...

Question 14

Describe the difference between reflected waves in these two cases: when the incident wave propagates from a less dense medium to a denser medium, and the opposite case, when the incident wave propagates from a denser medium to a less dense medium.

Accepted Answer

The answer of Describe the difference between reflected waves in...

Question 15

When a wave passes through a certain medium, the particles of the medium move with the wave. For example, a sound wave propagates through air via air molecules, which move from the source to receiver.

Accepted Answer

In a sound wave, the particles of the medium (such as air molecules) oscillate back and forth in the direction of the wave propagation, but they do not travel with the wave. The energy of the wave moves through the medium, while the particles themselves only experience local oscillations.

Question 16

Whenever a wave reflects off the boundary between denser and less dense medium, in any direction, it will result in an inverted wave.

Accepted Answer

When a wave reflects off a boundary from a denser to a less dense medium, it inverts. However, when reflecting from less dense to denser, it does not invert. The inversion depends on the direction of the density change at the boundary.

Question 17

An antenna 72.8 m long has a length equal to ¼ of a wavelength of the produced wave. If the station using this antenna emits a signal of 1030 kHz, what is the speed of the wave?

Accepted Answer

The answer of An antenna 72.8 m long has a...

Question 18

If we add two sine waves at the same point in space, the resultant has to have a larger amplitude than either of individual waves.

Accepted Answer

When two sine waves are added, the resultant amplitude can be larger, smaller, or the same as the individual waves, depending on their phase relationship. If they are out of phase, the amplitude can be smaller or even zero.

Question 19

A cello C-string vibrates in its fundamental mode with a frequency of 60 Hz. In order to tune it to a proper frequency of 65 Hz, how do you adjust the tension?

Accepted Answer

The answer of A cello C-string vibrates in its fundamental...

Question 20

Figure 14.6 Fig. 14.6 shows a sound wave. -What is the amplitude of the wave represented in Fig. 14.6? What are the wavelength and the frequency, assuming that it is a radio wave? The speed of the radio wave is 3 × 10⁸ m/s.

Accepted Answer