Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: scientizscht on 02/11/2019 11:44:24

Title: What is the smallest electro/magnetic field that can be detected precisely?
Post by: scientizscht on 02/11/2019 11:44:24

Hello

What is the smallest electro/magnetic field that can be detected with precision?

Thanks!

Title: Re: What is the smallest electro/magnetic field that can be detected precisely?
Post by: alancalverd on 02/11/2019 11:50:03

The human eye can detect about 5 visible photons. X-ray detectors respond to single photons. At low frequencies (low photon energies) the detection limit is set by the integration period required to distinguish the target signal from thermal noise, so the question is one of practical rather than theoretical limitation.

Title: Re: What is the smallest electro/magnetic field that can be detected precisely?
Post by: Bored chemist on 02/11/2019 12:00:34

A SQUID can measure magnetic fields smaller than those produced by the beating of your heat.
http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/Squid.html

https://en.wikipedia.org/wiki/SQUID

Title: Re: What is the smallest electro/magnetic field that can be detected precisely?
Post by: evan_au on 02/11/2019 21:41:45

Cryogenically cooled detectors on large telescopes can detect single photons that strike a CCD cell.

Unfortunately, the wiring and insulation between the CCD cells takes up some space on the surface of the chip, so they can't quite reach 100% photon efficiency.

See: https://en.wikipedia.org/wiki/Charge-coupled_device#Use_in_astronomy