Naked Science Forum

General Science => General Science => Topic started by: katieHaylor on 21/09/2017 16:23:25

Title: How do you measure the strength of a magnifying glass?
Post by: katieHaylor on 21/09/2017 16:23:25

Geoff asks:

How do you measure the strength of a magnifying glass?

Can you help?

Title: Re: How do you measure the strength of a magnifying glass?
Post by: RD on 21/09/2017 19:41:30

The power of a lens, in dioptre (https://en.wikipedia.org/wiki/Dioptre)s, is the reciprocal of the focal-length in metres ...
http://www.bbc.co.uk/bitesize/intermediate2/physics/waves_and_optics/power_of_lens/revision/1/

The focal-length is the distance between the lens & the cremated ant ...

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fstatic.tvtropes.org%2Fpmwiki%2Fpub%2Fimages%2Fant_burning_x.png&hash=5b6889cb7b5e673be3c0d0f1bd2fed82)

Title: Re: How do you measure the strength of a magnifying glass?
Post by: Bored chemist on 21/09/2017 19:54:22

However, that doesn't actually tell you the magnification.
I'm short-sighted. The lenses in my glasses are thinner in the middle than at the edge.
The make things look smaller, so the "magnification is some fraction between 0 and1.
But the power in dioptres is about  -10.

The magnification of a lens depends on how closely you can focus without it.

https://en.wikipedia.org/wiki/Magnification#Single_lens

Title: Re: How do you measure the strength of a magnifying glass?
Post by: evan_au on 21/09/2017 21:38:17

Quote from: OP

How do you determine the magnifying strength of a lens?

If you need great magnification (eg a microscope or telescope), you often use a compound lens, with multiple elements - calculating the magnification gets a lot more complex.

Designers of microscopes and telescopes will often sacrifice some magnification in order to reduce "chromatic aberration", colored fringes around the image.
See: https://en.wikipedia.org/wiki/Chromatic_aberration#Minimization

Title: Re: How do you measure the strength of a magnifying glass?
Post by: glot on 16/10/2017 11:16:56

I find the burning ant example offensive.

Title: Re: How do you measure the strength of a magnifying glass?
Post by: Bored chemist on 16/10/2017 17:43:05

Quote from: glot on 16/10/2017 11:16:56

I find the burning ant example offensive.

Do you have a problem with cremation?
I know some cultures prefer burials etc, but I don't think those requirements are usually applied to insects.