Ankit Gupta Posted February 6, 2014 Share Posted February 6, 2014 What the main "basic" difference between angular and linear magnification ? Link to comment Share on other sites More sharing options...
imatfaal Posted February 6, 2014 Share Posted February 6, 2014 The difference is that of measure; linear magnification is used when projecting an image on a screen and angular when viewing through an eyepiece. Linear Magnification is the ratio of the projected image size (measured with a ruler) over the actual size. Angular magnification is the ratio of the tangent of the angle subtended at the focal point of the eyepiece over the angle subtended at the focal point of the objective. Linear is clear and easy - but you cannot do a linear calcuation for a magnification system with an eyepiece as there is no screen so we use the ratio of the angles (or their tan) instead as this can be observed. If something without magnification covers 1 degree - with 5x Angular magnification it will appear to cover ~5 degrees (at low mag and angles you can almost ignore the tangent). Link to comment Share on other sites More sharing options...
Ankit Gupta Posted February 6, 2014 Author Share Posted February 6, 2014 But our retina also works as a screen and would u please explain it (angular magnification) with an example Link to comment Share on other sites More sharing options...
imatfaal Posted February 6, 2014 Share Posted February 6, 2014 But our retina also works as a screen and would u please explain it (angular magnification) with an example You need to investigate virtual images through an eyepiece. They are just ways of measuring things or more exactly quantifying a change - and how on earth would you go about measuring the image on a retina? 1 Link to comment Share on other sites More sharing options...
studiot Posted February 6, 2014 Share Posted February 6, 2014 ratio of the tangent of the angle subtended at the focal point of the eyepiece over the angle subtended at the focal point of the objective. Note that imatfaal said the tangent of one and the angle. We are assuming the small angle approximation here and further both should be tangents. There are three formulae, depending upon where the image is and its type. Are you studying these formulae The angular magnification is also known as the magnifying power. M and is defined as: [math]{\rm{M = }}\frac{{{\rm{visual}}\;{\rm{angle}}\;{\rm{subtended}}\;{\rm{by}}\;{\rm{image}}}}{{{\rm{visual}}\;{\rm{angle}}\;{\rm{subtended}}\;{\rm{by}}\;{\rm{object}}\;{\rm{when}}\;{\rm{viewed}}\;{\rm{directly}}}}[/math] 1 Link to comment Share on other sites More sharing options...
Ankit Gupta Posted February 7, 2014 Author Share Posted February 7, 2014 Note that imatfaal said the tangent of one and the angle. We are assuming the small angle approximation here and further both should be tangents. There are three formulae, depending upon where the image is and its type. Are you studying these formulae The angular magnification is also known as the magnifying power. M and is defined as: [math]{\rm{M = }}\frac{{{\rm{visual}}\;{\rm{angle}}\;{\rm{subtended}}\;{\rm{by}}\;{\rm{image}}}}{{{\rm{visual}}\;{\rm{angle}}\;{\rm{subtended}}\;{\rm{by}}\;{\rm{object}}\;{\rm{when}}\;{\rm{viewed}}\;{\rm{directly}}}}[/math] ya I know that formula and also what is angular magnification but the thing I want to know is how can I observe and differentiate b/w angular and linear magnification by seeing the image of an object by any lens Link to comment Share on other sites More sharing options...
studiot Posted February 7, 2014 Share Posted February 7, 2014 ya I know that formula and also what is angular magnification but the thing I want to know is how can I observe and differentiate b/w angular and linear magnification by seeing the image of an object by any lens What I gave before was a definition not a formula. The formulae connect measurable quantities (observables) like the focal length of the lens, the size of the object and its distance from the lens. If you know these formulae you can use them to deduce the size and therefore the magnification of the arrangement. In many applications the image is virtual or at infinity or both so the image distance is not an observable. I am not sure what you mean by 'differentiate between angular and linear magnification'. You measure the observables and use an appropriate formula to calculate the magnification required. In many cases the angular magnification reduces to the same as the linear. So you really do need to describe the setup for further information. Link to comment Share on other sites More sharing options...
Daft Blaze Posted October 19, 2016 Share Posted October 19, 2016 (edited) What I've been able to understand is that in linear magnification there is change in size/height of the object's image is such that both the object and image subtend the same angle at the optical centre whereas in angular magnification the size of the object and the image is the same, but the image subtends a greater (or smaller) angle at the optical centre, i.e. the object simply comes closer to you in a sense Edited October 19, 2016 by Daft Blaze Link to comment Share on other sites More sharing options...
AshBox Posted November 29, 2016 Share Posted November 29, 2016 I have read somewhere that, Linear magnification is the ratio of the size of object and image. Angular magnification is the ratio of the angle subtended by object and image. Subtended angles are related to the linear size by non-linear trigonometric functions and depend on the distance from image to eye. Link to comment Share on other sites More sharing options...
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