Physics – 6.2.3 The Universe | e-Consult

The redshift of light from a galaxy is a direct consequence of the Doppler effect. When a light source is moving away from an observer, the wavelengths of the light waves are stretched, resulting in a shift towards the red end of the spectrum. Conversely, if a light source is moving towards an observer, the wavelengths are compressed, resulting in a shift towards the blue end of the spectrum (blueshift).

The amount of redshift is directly proportional to the speed at which the galaxy is receding. The relationship can be expressed as:

v = zc

where:

• v is the recession velocity of the galaxy.
• z is the redshift value (a dimensionless quantity representing the fractional change in wavelength).
• c is the speed of light (approximately 3.0 x 10⁸ m/s).

A larger redshift value indicates a higher recession velocity. The redshift is determined by measuring the wavelength of light emitted by the galaxy and comparing it to the known rest wavelength of the same element. The difference in wavelength is then used to calculate the redshift value and, subsequently, the recession velocity.

[Image missing: Doppler Effect Diagram]