AP Physics 1 : Longitudinal and Transverse Waves

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #1 : Longitudinal And Transverse Waves

At a local concert, a speaker is set up to produce low-pitched base sounds with a frequency range of 20Hz to 200Hz, which can be modeled as  sine waves. In a simplified model, the sound waves the speaker produces can be modeled as a cylindrical pipe with one end closed that travel through the air at a velocity of , where T is the temperature in °C.

What type of waves are sound waves?

Possible Answers:

Electromagnetic

Gravitational

Transverse

Longitudinal

Correct answer:

Longitudinal

Explanation:

Sound waves are longitudinal waves, meaning that the waves propagate by compression and rarefaction of their medium. They are termed longitudinal waves because the particles in the medium through which the wave travels (air molecules in our case) oscillate parallel to the direction of motion. Alternatively, transverse waves oscillate perpendicular to the direction of motion. Common examples of transverse waves include light and, to a basic approximation, waves on the ocean.

Example Question #2 : Longitudinal And Transverse Waves

Which of these is an example of a longitudinal wave?

Possible Answers:

A sound wave

Visible light

Microwaves

X-rays

A wave produced by a rope oscillating in a plane

Correct answer:

A sound wave

Explanation:

Longitudinal waves transmit energy by compressing and rarefacting the medium in the same direction as they are traveling. Sounds waves are longitudinal waves and travel by compressing the air through which they travel, causing vibration.

Light, X-rays, and microwaves are all examples of electromagnetic waves; even if you cannot recall if they are longitudinal or transverse, they are all members of the same phenomenon and will have the same type of wave transmission. Transverse waves are generated by oscillation within a plane perpendicular to the direction of motion. Oscillating a rope is a transverse wave, as it is not compressing in the direction of motion.

Example Question #3 : Longitudinal And Transverse Waves

All of the following are transverse waves, except __________.

Possible Answers:

X-rays

sound waves

light waves

microwaves

Correct answer:

sound waves

Explanation:

An important distinction for the MCAT is the difference between transverse and longitudinal waves. Although both wave types are sinusoidal, transverse waves oscillate perpendicular to the direction of propagation, while longitudinal waves oscillate parallel to the direction of propagation.

The most common transverse and longitudinal waves are light waves and sound waves, respectively. All electromagnetic waves (light waves, microwaves, X-rays, radio waves) are transverse. All sound waves are longitudinal.

Example Question #4 : Longitudinal And Transverse Waves

Which of the following is not an example of a transverse wave?

Possible Answers:

Plucking a guitar string

An earthquake

Jumping up and down on one end of a rope bridge

A girl holding a jump rope moving her arm up and down

A break dancer doing "the worm"

Correct answer:

An earthquake

Explanation:

Transverse waves can be distinguished from longitudinal waves by the orientation of the oscillations to the direction of energy transfer. Transverse waves have oscillations perpendicular to the direction of energy transfer while longitudinal waves have oscillations parallel to the direction of energy transfer. The plucked guitar string may be tricky to think about because we use sound as a characteristic example of a longitudinal wave, and what does a plucked guitar string do but make sound? Well, the sound produced by the string is a longitudinal wave, but the string itself vibrates as a transverse wave. When the string is plucked, the energy is transferred down the string, yet the displacement is up and down or side to side. Meanwhile, an earthquake is a series of compressions that move underground due to shifting along a fault line for one. This is a longitudinal or compression wave. Another example of a transverse wave is those in the ocean. The wave oscillates vertically, causing rises and falls in the water level, but the waves are directed due offshore.

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