Doppler Effect (DP IB Physics: SL)

In the laboratory on Earth, hydrogen emits a spectral line that is measured by an observer to have a wavelength of 400 nm. The same spectral line is emitted by a galactic source that is moving away from Earth at speed of 0.2c, where c is the speed of light.

What is the wavelength of the same spectral line from the galaxy as measured by the observer on Earth?

A spectral line is observed at 530 nm in the laboratory. The same spectral line is observed in a galaxy which is receding from Earth at a velocity of 3.00 × 10⁶ m s⁻¹. 

What is the wavelength of the spectral line from the galaxy?

A star emits light of frequency . This light is observed on Earth to have a frequency  which is of a lower frequency than .

Which of the following correctly describes the speed and direction of motion of the star?

Two lines P and Q in the emission spectrum of a gas are measured on the Earth by a stationary observer.

The observer then moves towards the gas sample, and the emission spectrum is recorded as they are moving.

What is the correct pattern for the shifted spectral lines, P' and Q'?

Which of the following statements is true about redshift?

An alien living in another solar system sends a radio signal of frequency to the next planet in their solar system. The signal reflects back and is recorded as having a frequency  which is lower than the original signal.

A few days later they repeat the experiment and find that the frequency change is less than that observed in the first experiment.

Which of the following could cause these effect?

I. The atmosphere of the planet is rotating such that the radio beam reflects off a section that is moving away from the alien's planet 

II. The planet is moving away from the alien's planet

III. The atmosphere of the planet is rotating such that the radio beam reflects off a section that is moving towards the alien's planet 

IV. The planet is moving towards the alien's planet

In a binary star system, two stars orbiting each other can be observed using a spectrometer. The star system as a whole is moving away from the Earth at a constant velocity. The spectral lines appear to fluctuate. A graph can be plotted of relative velocity of each star compared to the observer.

At which point on the graph will the stars be in the following position?

Photographs of lines in the spectrum of the Sun show changes in wavelength. The atmosphere of the sun rotates at a speed , anti-clockwise as observed from its north pole.

What is an expression for the observed change in wavelength of a spectral line from light emitted from the right hand edge of the Sun as viewed from the northern hemisphere on the Earth?

Assume the Earth's orbit is circular.

The graph shows the dominant wavelength of light emitted by 4 different stars, and the same light observed from the Earth.

Which pair of stars are moving away from Earth at the same speed?