Gravitational radiospectrometer

TL;DR

This paper explores how gravitational lensing in plasma environments causes frequency-dependent bending of light, functioning similarly to a spectrometer, especially for very long radio waves near the plasma frequency.

Contribution

It introduces the concept of a gravitational radiospectrometer, analyzing how plasma affects lensing angles and their frequency dependence in gravitational fields.

Findings

Lensing angle depends on electromagnetic wave frequency in plasma.

Maximum effect occurs near the plasma frequency for long radio waves.

Potential applications in radio wave observations in astrophysics.

Abstract

Gravitational lensing is predicted by general relativity and is found in observations. When a gravitating body is surrounded by a plasma, the lensing angle depends on a frequency of the electromagnetic wave due to refraction properties, and the dispersion properties of the light propagation in plasma. The last effect leads to dependence, even in the uniform plasma, of the lensing angle on the frequency, what resembles the properties of the refractive prism spectrometer. The strongest action of this spectrometer is for the frequencies slightly exceeding the plasma frequency, what corresponds to very long radiowaves.