Redshift & Blueshift: Doppler Shift Explained Quiz

If z = (observed wavelength - rest wavelength) / rest wavelength, then z = (505 - 500) / 500; if z = 5 / 500, then the value is 0.01.

If there is no relative motion between the source and observer, then the observed wavelength equals the rest wavelength; if the difference is zero, then the redshift value (z) must be exactly zero.

If Hubble observed that distant galaxies are almost all redshifted, then it proved expansion; if the shift is proportional to distance, it led to Hubble's Law and eventually the discovery of accelerated expansion/Dark Energy.

If the light from an entire star is blended, and if different parts of the surface have different radial velocities, then the lines will smear out or "broaden" rather than just shift.

If the wave equation is v = frequency * wavelength, and if the velocity (v) of light is constant, then doubling the frequency must result in the wavelength being reduced by half to maintain the equation.

If cosmological redshift is caused by the stretching of the space between objects rather than the object's independent motion through space, then it is distinct from the standard Doppler effect studied in local astronomy.

If the Doppler effect detects velocity, it can measure galaxy spin, planetary wobbles, and sirens; however, chemical composition is determined by the presence of specific lines (spectroscopy), not their shift.

If two stars are orbiting each other, one will be blueshifted while the other is redshifted; if they both contribute light to the spectrum, then the shared spectral lines will appear to double or split.

If high velocities affect the passage of time according to Einstein's theories, then the standard linear Doppler formula becomes inaccurate and the relativistic version must be applied.

If the Doppler effect only measures the compression or stretching of waves along the line of sight (radial motion), then it cannot detect motion occurring at a 90-degree angle (transverse) to the observer.

If a source is moving away while emitting waves, then each successive wave crest is emitted from a position further than the last; if the distance between crests increases from the observer's perspective, then the observed wavelength increases (redshift).

If the Doppler effect is caused by relative motion, then the star's speed, Earth's speed, and the star's rotation all contribute; distance itself does not change the shift percentage, but cosmic expansion (cosmological redshift) does.

If we need to see the displacement of tiny dark lines in a spectrum, then we must use a device that disperses light into its component wavelengths; that device is a spectrograph.

If the lines move toward longer wavelengths, and if red light has the longest wavelengths in the visible spectrum, then the shift is by definition a redshift, indicating the source is receding.

If the second postulate of Special Relativity states that the speed of light in a vacuum is constant (c) for all observers, then the star's motion only affects the frequency and wavelength of the light, never its velocity.

If we need to know how much a wavelength has shifted, then we must know its original position; if elements like Hydrogen emit specific wavelengths in a lab on Earth, then those lab values serve as the stationary "rest" reference.

If the basic Doppler equation is v = c * (delta lambda / lambda), then the calculation mathematically requires the change in wavelength, the original wavelength, and the universal constant for light speed.

If a planet orbits a star, it exerts a gravitational tug; if the star moves in a small orbit around the system's barycenter, then we can use the Doppler effect to detect the star's changing radial velocity.

If the Doppler effect only accounts for motion along the line of sight, and if "radial" describes motion directly toward or away from a point, then the calculated speed is the radial velocity.

If an object moves toward the observer, the emitted light waves are compressed into a smaller spatial interval; if shorter wavelengths are associated with the blue end of the visible spectrum, then the object is "blueshifted."