# Homework Help: Convex mirror question

1. Jul 25, 2016

### Brittany King

1. The problem statement, all variables and given/known data

A convex spherical mirror with a focal length of magnitude 25 cm has a 4.0-cm tall flower placed 100 cm in front of it. What is the height of the image of the flower?

a.20 cm
b. 1.6 cm
c .0.80 cm
d. 4.0 cm
e. 8.0 cm

2. Relevant equations

1/f=1/do+1/di

M=-di/do=hi/ho

3. The attempt at a solution

Using mirror equation I calculated di=33.3cm
Using Magnification equation I calculated hi=1.33cm

I thought this would be a simple problem, I don't see my mistake. Do any of you? Thanks in advance.

2. Jul 25, 2016

### BvU

3. Jul 25, 2016

### yihloong

you have used the correct equations, but you forget about the focal length of convex mirror is virtual, hence you should substitutes f = -25 cm, and you should get di = -20 cm , hence, hi = 0.80 cm

4. Jul 25, 2016

### BvU

Hello yihloong,

Please note that in PF we don't provide the answers: we help the posters learn and understand by pointing at mistakes and by asking relevant questions. Directly giving an answer often robs the poster from a valuable learning experience