Alberta Grade 8 Science – Light and Optical Systems Practice Test

Long-wavelength electromagnetic radiation, like radio waves and microwaves, can pass through thick dust that blankets dense interstellar clouds. This lets us see inside regions where stars form, where visible light would be blocked. In these radio wavelengths, astronomers also measure how gas moves by observing Doppler shifts in spectral lines, which tell us the speed and direction of the gas. Gamma rays come from high-energy processes and aren’t the right tool for studying cold, dark gas in dusty clouds. Ultraviolet and visible light are easily blocked by dust, so they don’t reveal the interior. So the best description is radio waves and microwaves.