Go Back   Physics Help Forum > High School and Pre-University Physics Help > Light and Optics

Light and Optics Light and Optics Physics Help Forum

Reply
 
LinkBack Thread Tools Display Modes
Old Apr 24th 2015, 07:24 AM   #1
Junior Member
 
Join Date: Apr 2015
Posts: 1
Mirrors! I need help I have a quiz tonight!

I have a physics test tonight and I really need help with this one problem!
This is what I've tried:

Your sister is standing in front of a convex mirror, trying on ninja masks. The distances dsister is 46.9 inches. The distance from the mirror to the virtual image is 13.35 inches. What is the distance from your sister to the mirror's focal point, in inches? Give your answer to three decimals.


(1/di+1/do)^-1=f > (1/46.9+1/13.35)^-1=10.39195029747

f+do=57.29195029747

The Practice Quiz answer is 65.562.

Am I skipping a step?

Update: dsister is do

Last edited by fisikschick; Apr 24th 2015 at 07:39 AM.
fisikschick is offline   Reply With Quote
Old Apr 24th 2015, 09:59 AM   #2
Senior Member
 
Join Date: Apr 2015
Location: Somerset, England
Posts: 1,035
I made it 65.5".

But then, I realised that a virtual image is negative in the lens formula.

Last edited by studiot; Apr 26th 2015 at 10:13 AM.
studiot is offline   Reply With Quote
Reply

  Physics Help Forum > High School and Pre-University Physics Help > Light and Optics

Tags
geometric optics, mirrors, need help!, quiz, tonight



Thread Tools
Display Modes


Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
NETW 589 Quiz Week 1 DeclanLay General Physics 0 Jan 23rd 2016 09:33 AM
online quiz due tomorrow help! tj09 Equilibrium and Elasticity 0 Nov 8th 2010 08:03 PM
Quiz Review.. reminisce2k7 General Physics 0 Jan 17th 2010 03:53 PM
mirrors hawaii Advanced Optics 1 Nov 22nd 2009 08:04 PM
Help me PLZ I NEED IT BY TONIGHT!! jkhwun Light and Optics 1 Jun 14th 2009 06:27 PM


Facebook Twitter Google+ RSS Feed