# Understading the strain

**URL:** <https://ask.igwn.org/t/understading-the-strain/294>\
**Category:** Science Questions\
**Created:** [May 24, 2022, 1:54pm UTC](https://ask.igwn.org/t/understading-the-strain/294 "2022-05-24T13:54:24Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![gaba](https://avatars.discourse-cdn.com/v4/letter/g/e0b2c6/32.png) [@gaba](https://ask.igwn.org/u/gaba)\
**Post date:** [May 24, 2022, 1:54pm UTC](https://ask.igwn.org/t/understading-the-strain/294/1 "2022-05-24T13:54:24Z")

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Hello everybody!  
I’m having a hard time in understanding some basic things about GW. For example, the waveform that the detectors obtain are h vs. t plots, right? Is it correct to say that the strain h is like a dimensionless amplitude of the GW? I get it when it says that h=Delta L/L because that is the effect on the detectors, but intrinsically to the wave…is it really its amplitude? Does it have to do somehow with the perturbation h\_ij?

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**Author:** ![jonah](https://yyz1.discourse-cdn.com/flex031/user_avatar/ask.igwn.org/jonah/32/10_2.png) [@jonah](https://ask.igwn.org/u/jonah)\
**Post date:** [May 24, 2022, 2:38pm UTC](https://ask.igwn.org/t/understading-the-strain/294/2 "2022-05-24T14:38:54Z")

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Hi @gaba

Yes - that’s right. The “strain” is directly related to the metric perturbation. There are lots of textbooks and papers that try to describe this relationship. For example, you might try [this paper](https://iopscience.iop.org/article/10.1088/1367-2630/7/1/204/pdf), especially around equations 3.5 and 3.6.

Or, a favorite for many people is [Peter Saulson’s book](https://www.thriftbooks.com/w/fundamentals-of-interferometric-gravitational-wave-detectors_peter-r-saulson/14547034/item/33869704/?gclid=Cj0KCQjwhLKUBhDiARIsAMaTLnH56DR-QgZFYmkcOIPanvuJQJBhXggXOa0-oLeiTiSYntpj1_yF7uoaAjgSEALw_wcB#idiq=33869704&edition=15435796).

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**Author:** ![gaba](https://avatars.discourse-cdn.com/v4/letter/g/e0b2c6/32.png) [@gaba](https://ask.igwn.org/u/gaba)\
**Post date:** [May 24, 2022, 2:44pm UTC](https://ask.igwn.org/t/understading-the-strain/294/3 "2022-05-24T14:44:05Z")

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Oh great! Thank you!!! 🙂