1HINT: define pole of a mirror and how to find it
A object is kept at a point (40,20√3) in front of a concave mirror of radius=20. find magnification of image. (its not just 1/v+1/u=1/f !!!!)
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9this is a easy q if u had posted a figure ith power , the language is misleading wen u say CENTRE at 20,0 many take it as pole
without realising that its CENTRE OF CURVATURE of mirror !!!
1i have not taken into account that fact!!
two thngs are always true:
1) ray passing through pole, reflects at the same angle with the principal axis.
2) ray passing through focus afetr reflection , is parallel to the p-axis..
only problem (the biggest prob) with this method is .. it has too much of geometry n so its time taking...
1iHEY I WAS SOLVING THE QUESTION WITH WRONG DATA!!!!
THE "CENTER" you mentioned , i took it as the pole!! :(
1p.s. ABOUT AUTHENTICITY OF SOLUTION
"it was a FTSE interview question"
1Solution:
Basically, you have to identify the POLE OF MIRROR. why? because then opnly you get to know what is u. now i have to make the rays paraxial. so i have to take the point P as pole where p is the intersection of the imaginary spherical surface of mirror and the st. line through object and center. check yourslf:
u=√(202+(20√3)2) + 20.
= 60,
then v= 12. along the prev. mentioned st. line. so pos. of image
16,-4√3
1tis is wat came to my mind at the very first jus afet rreading the question... dat the rays aree not paraxial....
ifwe complete the srphere for that mirror .. then actulaly we have the point object above the sphere (20root3.. dats it..)
bt the exact thing is not clicking ....
1ok ok, if it is a point object no question of magnification arise, but what i ask to find is image of the tip. and i mentioned mirror formula can not be directly used unless you do something to make the rays PARAXIAL
1if u are asking the magnification then it should be 1
otherwise if u are asking the final distance of image from the principal axis
then it can be easily found out with the mirror formulas
1sorry i forgot to mention centre is at 20,0. the object's projection on xaxis is 40,0 the point on mirror where axis cuts it is origin.it is same as when you take sign convention
1sorry i forgot to mention centre is at 20,0. the object's projection on xaxis is 40,0 the point on mirror where axis cuts it is origin.it is same as when you take sign convention