(adsbygoogle = window.adsbygoogle || []).push({}); [SOLVED] Short optics question

Shiny lawn spheres placed on pedestals are convex mirrors. One such sphere has a diameter of 42 cm. A 13 cm robin sits in a tree 2.1 m from the sphere.

(a) Where is the image of the robin? in cm

b) How long is the robin's image? in cm

1/f=1/do+1/di

hi/ho=-di/do

Ok, I know that radius of a concave lens is 2f but when i use that principle i do not get the right answer...what i did is:

42/2=21=radius

21/2=10.5=focal length

1/10.5=1/210+1/x

x=11.0526 which was my answer for a which webassign says is wrong

once i get this answer part b is very easy as all i will have to do is x/13=-answer to part a/210

plz help me figure out what i did wrong im assuming that radius of a convex lens which is what is used in problem is not 2f but i have no clue what it is then and i tried googling it but could not find anything...thanks

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# Homework Help: Short optics question

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