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# Unit 3: How do we know that the universe is expanding?

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We studied the motion of objects oscillating in isolation. What happens in a system, which is a collection of such objects?

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- Identifying transverse and longitudinal wavesGet 3 of 4 questions to level up!

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- Understand: wave propertiesGet 3 of 4 questions to level up!
- Properties of transverse and longitudinal wavesGet 3 of 4 questions to level up!
- Apply: wave propertiesGet 3 of 4 questions to level up!
- Understand: mechanical waves and lightGet 3 of 4 questions to level up!
- Understand: mechanical wavesGet 3 of 4 questions to level up!
- Calculating frequency and wavelength from displacement graphsGet 3 of 4 questions to level up!

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- Doppler effectGet 3 of 4 questions to level up!

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- Wave interference - 1Get 3 of 4 questions to level up!
- Wave interference - 2Get 3 of 4 questions to level up!
- Connection between path and phase differenceGet 3 of 4 questions to level up!
- Construction and destruction of interfering wavesGet 3 of 4 questions to level up!

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- Wavelength of standing wavesGet 3 of 4 questions to level up!
- Calculating frequency for harmonics of a standing waveGet 3 of 4 questions to level up!
- Wavelength and frequency for sound waves in tubes Get 3 of 4 questions to level up!
- Pressure and displacement of sound waves in tubesGet 3 of 4 questions to level up!

Level up on the above skills and collect up to 320 Mastery points

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