Question

The spectrum of a star’s light is measured and the wavelength of one of the lines as the sodium’s line is found to be 589 nm. The same line has the wavelength of 497 nm when observed in the laboratory. This means the star is:

Options

A
Moving away from the earth
B
Moving towards the north
C
Stationary
D
Revolving around the planet

Explanation

When the wavelength of star was measured it resembled to the wavelength of sodium having wavelength 589 nm and when the sodium line was observed in the lab, its wavelength was calculated it came out to be 497nm . this means the wavelength had increased and it increases when star moves away.

When the wavelength of star was measured it resembled to the wavelength of sodium having wavelength 589 nm and when the sodium line was observed in the lab, its wavelength was calculated it came out to be 497nm .This means the wavelength had increased and it increases when star moves away.

This option is incorrect because the change in wavelength (Doppler shift) indicates a change in radial velocity along the line of sight, not in a specific direction like north.

This option is incorrect because the difference in wavelengths indicates a Doppler shift, which usually occurs due to motion, not when an object is stationary.

This option is incorrect because the observed spectral shift is indicative of radial velocity along the line of sight, which doesn't directly relate to an object revolving around a planet.