heres the problem:(adsbygoogle = window.adsbygoogle || []).push({});

a dentist wants a small mirror that, when 2.20cm from a tooth, will produce a 4.5x upright image. what kind of mirror must be used and what must its radius of curvature be?

so i did the following calculations with the mirror equations i learned:

m=4.5

equation to get the di https://www.physicsforums.com/attachment.php?attachmentid=7885&stc=1&d=1159712057

4.5*(-2.20) = di di=-9.9

1/do+1/di=1/f

1/(-2.2) + 1/(-9.9) = 1/f

1/(-2.2)=(-0.454545455)

1/(-9.9)=(-0.101010101)

(-0.454545455)+(-0.101010101)=(-0.555555556)

1/(-0.555555556)=f

1/(-0.555555556)=(-1.8)

f=(-1.8)

f2 = r

-1.8 * 2 = -3.6

so the radius is -3.6 and i guess it is concave as only concave mirrors 1.0+ magnify? that's wrong as my book says the correct answer is 5.66cm, concave. what am i doing wrong

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Trouble with mirror equations, need help.

**Physics Forums | Science Articles, Homework Help, Discussion**