Self Check: Mediums, Speed, and Distances

Which of the following materials would sound travel fastest through?

• a wooden desk

• a sponge

• a beaker of water

• the air in the room

Answer explanation

The speed of a mechanical wave is faster in MORE DENSE mediums.

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(SC.7.P.10.3) Mechanical Wave Speed

Which of the following materials would light travel fastest through?

• Plastic

• Air

• Water

• Light waves travel the same in each one

Answer explanation

Electromagnetic waves travel faster in LESS DENSE mediums.

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(SC.7.P.10.4) Electromagnetic Wave Speed

How does the speed of light in water compare to its speed in air?

• The speed is the same in water because it is constant in all mediums.

• The speed is faster in water than in air because the molecules are closer together.

• The speed is slower in water than in air because the molecules are closer together.

• The speed cannot be compared without knowing the temperature.

Answer explanation

Electromagnetic waves travel faster in LESS DENSE mediums.

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(SC.7.P.10.4) Electromagnetic Wave Speed

Why can't sound travel in space?

• Sound is a mechanical wave, because of this it cannot travel in a vacuum.

• Sound is a mechanical wave, because of this it cannot travel in a medium.

• Sound is a electromagnetic wave, because of this it cannot travel in a vacuum.

• Sound is a electromagnetic wave, because of this it cannot travel in a medium.

Answer explanation

The distance from the sun to Earth is called an AU. All objects in our solar system are within 140 AU of the sun.

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(SC.8.E.5.1) Vastness of Space

Sound waves travel at different speeds through different materials. Through which of the following materials

will sound waves travel the fastest?

• copper pipe

• swimming pool

• air on a cold day

• sauna filled with steam

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(SC.7.P.10.3) Mechanical Wave Speed

Sound waves and light waves behave differently in different materials. How are sound waves different from light waves?

• Sound waves cannot travel through a vacuum.

• Light waves cannot travel through a vacuum.

• Only sound waves can pass through a material.

• Only light waves can pass through a material.

Answer explanation

Mechanical waves are caused by collisions of matter. No matter = No collisions = No wave.

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(SC.7.P.10.3) Mechanical Wave Speed

What happens to the speed of a sound wave as it passes from the air into the ground?

• it decreases

• it increases

• it remains constant

• it immediately stops

Answer explanation

Mechanical waves move faster in denser mediums, the ground is denser so the sound would go faster.

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(SC.7.P.10.3) Mechanical Wave Speed

Which of the substances in the table would an electromagnetic wave, like X-ray light, travel through the fastest?

• air

• body fat

• skull bone

• copper

Answer explanation

X-rays are electromagnetic waves, electromagnetic waves travel fastest through low density mediums.

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(SC.7.P.10.4) Electromagnetic Wave Speed

Which medium would an electromagnetic wave travel through at the lowest speed?

• Vacuum

• Air

• Quartz

• Diamond

Answer explanation

Electromagnetic waves move slower through denser mediums.

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(SC.7.P.10.4) Electromagnetic Wave Speed