Test: Waves, Wave Motion and Types of Waves - Grade 11 MCQ

A wave is defined as a vibratory disturbance that carries energy from one point to another without the actual movement of the medium itself. This is evident in various types of waves, including mechanical and electromagnetic waves.

In wave motion, the disturbance travels through the medium, but the medium itself does not move along with the disturbance. This can be illustrated by the ripples formed in water when a stone is thrown in.

Mechanical waves, such as sound waves and water waves, require a medium (solid, liquid, or gas) to propagate. In contrast, electromagnetic waves do not require a medium.

The key distinction is that in transverse waves, particle displacement is perpendicular to the direction of wave propagation, whereas in longitudinal waves, it is parallel. This is evident in how sound waves (longitudinal) and waves on strings (transverse) behave.

Audible sound waves are defined as those with a frequency range between 20 Hz and 20,000 Hz. Frequencies below this range are termed infrasonic, and those above are ultrasonic.

Sound waves are indeed mechanical longitudinal waves that require a medium, such as air, water, or solids, for propagation. They cannot travel through a vacuum.

The velocity of sound in a gas increases with the square root of its absolute temperature. This is because higher temperatures increase the energy and movement of particles in the medium, facilitating faster wave propagation.

A pressure node corresponds to points in a standing wave where pressure changes are minimal. This occurs at points of maximum displacement where the amplitude is highest.

For a closed pipe, the wavelength is related to the harmonic number by the formula Length = 4λ/n, where n corresponds to the harmonic number. This indicates how the length of the pipe determines the wavelengths of the sound waves it can produce.

Increased humidity in the air results in a higher speed of sound. Water vapor is less dense than dry air, allowing sound waves to travel faster through humid air.

When a wave reflects off a fixed boundary, it undergoes a phase change of π (or 180 degrees) to satisfy the boundary condition of zero displacement at that point.

The minimum distance between a node (where displacement is zero) and an antinode (where displacement is maximum) in a standing wave is λ/4.

At constant temperature, the velocity of sound in a gas does not depend on pressure, as the ratio of pressure to density remains constant.

Only transverse waves can be polarized because their oscillations occur in a direction perpendicular to the direction of wave propagation, allowing for selective orientation of the wave's oscillation direction.

Sound waves are classified as longitudinal waves because the displacement of air molecules occurs in the same direction as the wave propagation, resulting in compressions and rarefactions.

The speed of sound increases when it travels from air into water because water is denser and more elastic than air, allowing sound waves to travel faster.

Ultrasonic waves are sound waves with frequencies greater than 20,000 Hz. These waves are commonly used in medical imaging and industrial applications.

The speed of sound in gases is inversely proportional to the square root of the density. As density increases, the speed of sound decreases due to the added mass that the wave must move through.

Matter waves are associated with particles such as electrons and protons and are described by quantum mechanics. They do not require a medium for propagation and are fundamental in modern physics.