Most Repeated MDCAT Physics: Wave Motion and Sound MCQs

Explanation

Given: v (receding speed) = 1.40 x 10^7 m/s f_source (emitted frequency) = 4.57 x 10^14 Hz c (speed of light) = 3.0 x 10^8 m/s Doppler effect formula for light: f_observed = f_source * sqrt((1 - v/c) / (1 + v/c)) Calculations: v/c = (1.40 x 10^7 m/s) / (3.0 x 10^8 m/s) = 0.0466666... sqrt((1 - v/c) / (1 + v/c)) = sqrt((1 - 0.0466666...) / (1 + 0.0466666...)) sqrt((1 - v/c) / (1 + v/c)) = sqrt(0.9533333 / 1.0466666) sqrt((1 - v/c) / (1 + v/c)) = sqrt(0.9108108) sqrt((1 - v/c) / (1 + v/c)) = 0.9543641 (approximately) f_observed = 4.57 x 10^14 Hz * 0.9543641 f_observed = 4.361936 x 10^14 Hz Result: f_observed = 4.

Explanation

Light waves are electromagnetic waves that do not require a material medium to travel. They can travel through a vacuum, as demonstrated by sunlight reaching Earth from the Sun.

Explanation

Doppler's effect applies to all options (A, B, C). It describes the change in frequency of waves due to relative motion between the source and observer. For sound, it's apparent in pitch shifts; for radio and electromagnetic waves, in frequency shifts affecting observed wavelength.

Explanation

The carrier signal is a sine wave at the carrier frequency. The sine wave has three characteristics that can be altered. The term that may be varied is the carrier voltage Ec, the carrier frequency FC, and the carrier phase angle θ. So three forms of modulations are possible.

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The applications of doppler effects are tracking satellite, measuring speed of automobile by traffic police, sending radar signals, VOR, homosonde, sonar and spectral analysis of light emitted by stars.

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In air column and wind instruments, longitudinal waves produce superposition. Hence, option D is correct.

Explanation

As v= fλ So the product of frequency and wavelength is equal to speed of wave.

Explanation

Option C is correct.The distance between two consecutive nodes or antinodes is half of the wavelength. A node is a point on a standing wave where the displacement is zero. An antinode is a point on a standing wave where the displacement is maximum. The distance between two consecutive nodes or antinodes is half of the wavelength λ/2 because the wavelength is the distance between two consecutive points on a wave that is in the same phase.

Explanation

Waves that do not require any medium for their propagation are called electromagnetic waves.

Explanation

The correct answer is D, "All of the above" because the wave velocity in any medium depends on all of these factors: elasticity, density, and homogeneity. - Elasticity affects how well a material can transmit mechanical waves. More elastic materials allow for faster wave propagation. - Density plays a role because waves travel at different speeds through materials with different densities. For example, sound waves travel faster in denser materials. - Homogeneity refers to the uniformity of a medium. A more homogeneous medium allows for more consistent wave propagation.

Explanation

No. of loops in stationary waves depend on frequency of waves.

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The diffraction of sound waves around a corner is noticeable. Therefore, sound can be heard around corners but cannot be seen.

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A node is a point along a standing wave where the wave has minimum amplitude. All the particles of the string execute SHM except nodes.

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The molecular theory for metals is also called as band theory. Band theory is a quantum mechanical model that describes the behavior of electrons in solids. It is based on the idea that the electrons in a solid can be grouped into bands, which are ranges of energy levels that the electrons can occupy. In metals, the valence electrons (the electrons in the outermost shell) are delocalized, which means that they are not bound to any individual atom. Instead, they are free to move throughout the metal. This is why metals are good conductors of electricity.

Explanation

A wave is typically characterized by the following physical parameters:1. Wavelength (λ): The distance between two consecutive points on the wave that are in phase with each other.2. Frequency (f): The number of oscillations or cycles of the wave per second.3. Speed of wave (v): The distance traveled by the wave per unit time.

Explanation

The factor that does not significantly affect the speed of sound in air (under normal conditions) is pressure of gas. Here's why:Temperature: The speed of sound in air is directly proportional to the square root of the absolute temperature. As temperature increases, the speed of sound increases. This is the most significant factor. Moisture in air (Humidity): Increased humidity slightly increases the speed of sound. This is because lighter water molecules replace some of the heavier nitrogen and oxygen molecules in the air, slightly decreasing the density.Density of gas: In general, the speed of sound is inversely proportional to the square root of the density of the medium.

Explanation

Beat frequency i.e,number of beats per second is equal to the difference between the two combining frequencies. Hence, there will be 250-245= 5 Hz.

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A longitudinal wave is a type of wave that travels in the direction of the medium, but a transverse wave is another type of wave that travels in the direction of the medium.So the correct option is A.

Explanation

Destructive interference at a point between the two waves takes place if the path difference between the waves at that point is equal to odd integral multiple of half wavelength of the wave.So, path difference Δx=(n+1/2)λWhere n must be an integer.