Concave mirror positioning help

AI Thread Summary
A concave shaving mirror with a radius of curvature of 40 cm produces an upright image that is 3.30 times larger than the actual face. The user initially calculated the distance from the mirror to the face as 26.1 cm but later corrected it to 13.94 cm. The equations used were the magnification formula and the mirror equation. The discussion highlights the importance of correctly applying these equations to solve for the distance. The final answer provided is 13.94 cm.
I_LuV_FiZiX
Messages
27
Reaction score
0

Homework Statement


A concave shaving mirror has a radius of curvature of 40 cm. It is positioned so that the (upright) image of a man's face is 3.30 times the size of the face. How far is the mirror from the face?


Homework Equations


M = Si/S 1/S + 1/Si = 2/R


The Attempt at a Solution


I have 2 equations with 2 unknowns. I isolated Si in the first one and substituted this expression into equation 2 to find S. I get an answer of 26.1cm.

The computer keeps telling me I'm wrong though. Could someone check my math or tell me if my equation setup is correct?
 
Physics news on Phys.org
oops never mind i got it... 13.94cm
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Position of Final Image in Concave Mirror with Glass Block
Replies
13
Views
3K
I Understanding magnification of concave mirrors for near-eye situation?
Replies
11
Views
2K
Location of object on axis of concave mirror?
Replies
4
Views
2K
Placing object between 2 spherical mirrors
Replies
3
Views
2K
How Do You Calculate the Focal Length of a Concave Mirror with a Moving Image?
Replies
13
Views
3K
How to solve for distance of object with a concave mirror?
Replies
1
Views
2K
Is the Solution for Rotation of Spherical Mirrors Incorrect?
Replies
16
Views
1K
The size of the image of the Sun
Replies
1
Views
1K
What Is the Focal Length of the Concave Lens in This Lens-Mirror Combination?
Replies
1
Views
2K
Image formed by a plane-concave lens and a concave mirror
Replies
1
Views
2K

Hot Threads

Recent Insights

Back
Top