The correct answers to fill in the blanks are:
- When a vibrating object is moving toward an observer, the measured frequency of the vibrations will be higher than if the object and observer are both stationary.
- If the vibrating object is moving away from an observer, the measured frequency of the vibrations will be lower than the actual rate of vibration of the object.
- When a star is moving towards an observer on Earth, the light spectrum of the star will appear blueshifted compared to the light spectrum of the sun, which is considered to be in Earth's frame of reference.
So the completed sentences are:
- When a vibrating object is moving toward an observer, the measured frequency of the vibrations will be higher than if the object and observer are both stationary.
- If the vibrating object is moving away from an observer, the measured frequency of the vibrations will be lower than the actual rate of vibration of the object.
- When a star is moving towards an observer on Earth, the light spectrum of the star will appear blueshifted compared to the light spectrum of the sun, which is considered to be in Earth's frame of reference.