Electromagnetic vs Mechanical Waves

Which state of matter do sound waves move fastest through?

• Solid

• Liquid

• Gas

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NGSS.MS-PS4-1

NGSS.MS-PS4-2

Thinking back to the video, why does sound travel slower in a gas?

• The particles in a gas are so far apart, so it is harder for them to bump the next particle to pass along the energy

• The particles in a gas are so close together, so it is harder for the energy to move in between the particles

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NGSS.MS-PS4-1

True or False: Light can travel with or without a medium.

• True

• False

Where do light waves travel the fastest?

• Solid

• Liquid

• Gas

• A vacuum

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NGSS.MS-PS4-2

Think of the people in these images as particles. Which image represents where light would be able to move the quickest down the street?

• Picture 1 (no people)

• Picture 2 (crowded with people)

Answer explanation

Particles get in the way of light waves, slowing them down. In picture 2, the crowd of people would make it difficult to see the sunlight on the other side of the street.

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NGSS.MS-PS4-2

Think of the people in these images as particles. Which image represents where sound would be able to move the quickest down the street?

• Picture 1 (no people)

• Picture 2 (crowded with people)

Answer explanation

Sound waves need the particles to transfer their energy, so the more particles the better. This is like Picture 2 being an easier place to find someone to whisper to.

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NGSS.MS-PS4-2

What type of wave is a sound wave? (select two)

• Electromagnetic

• Mechanical

• Transverse

• Longitudinal

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NGSS.MS-PS4-2

What type of wave is a light wave? (select two)

• Mechanical

• Electromagnetic

• Transverse

• Longitudinal

Compared to the speed of light, sound travels______.

• slower

• the same

• faster

• it depends on the circumstance

Answer explanation

The speed of light moves 1 million times faster than the speed of sound.

What would happen to the speed of a light wave as it travels from oil to a diamond?

• Speeds up

• Slows down

• Stay the same

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NGSS.MS-PS4-2