A candle is placed 1.8 m from a screen. whereshould a lens of focus length 21 cm (0.21 m) be placed between the screen and the candle to prduce a sharp image screen?(adsbygoogle = window.adsbygoogle || []).push({});

The only formula i could think of was 1/f=1/do+1/di

I've now spent 3 hours on this (test tomorrow) and still don't know where to start. I have that first formula and the only other formula we've used had to do with magnification and object height. I am truly lost.

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

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: Grade 11 optics

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