Introduction to Wave pt 3: EM vs Mechanical Waves

Introduction to Wave pt 3: EM vs Mechanical Waves

by Ms Taylor

​Types of Waves

• Waves may be categorized based on whether or not they need a medium.

• ​There are two types of waves:

  • 1.) Mechanical waves: require a medium (matter) to travel.

    2.) Electromagnetic (EM) waves: do NOT require a medium to travel.

​Mechanical waves

• ​These require a medium for the vibrations to travel and so cannot travel through space (vacuum)

• ​

• ​May either move as transverse or longitudinal waves.

• ​

• ​Ex. sound, water wave, slinky,

​​Mechanical waves

• ​The speed at which they travel depends on either the type of wave or the medium they are in.

• ​

• ​They travel fastest in more dense medium. Therefore, they move fastest in solids and slowest in gases.

• ​

• ​Generally, these have longer wavelengths than electromagnetic waves.

​Electromagnetic Wave

• ​A waves that does NOT require a medium (matter to travel), has an electric field component and a magnetic field component.

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• ​These two fields move perpendicular to the propagation of the wave and so they are all transverse waves

​Electromagnetic waves

• ​All electromagnetic waves travels at the speed of light 3.0 x 10⁸ m/s in a VACUUM. However, they travels at different speeds when traveling through matter.

• They travel fastest in less dense medium, so fastest in gases and slowest in solids.

• Ex: Radio waves, Microwaves, Infrared, Visible Light, Ultraviolet, X-rays, and Gamma Ray.

​Electromagnetic Spectrum

• ​Shows a visual display of various electromagnetic waves to compare their relative wavelengths and frequencies.

Multiple Choice

Which type of waves must have a medium in order to travel?

• electromagnetic wave

• mechanical wave

Multiple Choice

Mechanical waves usually travel fastest through:

• solids

• liquids

• gases

Multiple Choice

What type of wave is this?

• Electromagnetic

• Mechancial

• Both Electromagnetic and Mechanical

Multiple Choice

A microwave is an example of what type of wave?

• electromagnetic wave

• mechanical wave

Multiple Choice

A water wave is an example of what type of wave?

• electromagnetic wave

• mechanical wave

Multiple Choice

Wave with the longest wavelength

• microwave
• radio
• gamma
• visible light

Multiple Choice

When the wavelength increases the frequency will

• increase

• decrease

• remain same

• none of these

Multiple Choice

EM waves  

• Must travel through a vacuum
• Can travel through a medium or a vacuum
• Are the same type of wave as mechanical waves
• Can only travel through a vacuum

Multiple Choice

All electromagnetic waves have the same...

• frequency
• speed
• wavelength
• energy

Multiple Choice

When a wave is travelling through matter, what happens to the matter?

• The matter is pulled along behind the wave as that makes it a longitudinal wave.

• The wave is making the matter move back and forth as that will make a transverse wave.

• The wave is making the matter move up and down.

• The matter is pulled along behind the wave as that makes it a compressional wave.

• The matter does not move along with the wave.

Multiple Choice

It depends on the medium in which the wave is traveling. It varies in solids, liquids and gases.

• Frequency

• Wave speed

• Amplitude

• Wavelength

Multiple Choice

Which wave in the diagram has the greatest wavelength?

• 1

• 2

• 3

• 4