Question

Neutral hydrogen atoms are moving along the axis of a vacuum tube with a speed of
2.0 × 106 ms−1. A spectrometer receives light emitted by these atoms in the direction
of their forward motion. If emitted from hydrogen atoms at rest, this light would
have a measured wavelength of 486.13 nm. Calculate the expected wavelength for
light emitted from the approaching atoms, using the relativistic formula.