Solving the Concave Lens Problem for a Hotel Room Peephole

[itsgood819]

A certain 0.86 cm lens is used in a peephole for hotel room doors for safety reasons. The tenant sees the maid in the peephole but she is reduced in size by a factor 0.01.

A. What type of lens must be used?
B. Where is the image of the maid located?
C. What is the power of this lens?


The attempt at a solution
From the given, I assumed it was a concave lens. Focal length would equal 0.86 cm, and magnification would equal 0.01? How would I do part B? I started out using the m= -d_i/d_o but got stuck.

Also, what is the equation for the power of lens?

Thank you for your help!

 

[ideasrule]

From the given, I assumed it was a concave lens. Focal length would equal 0.86 cm, and magnification would equal 0.01? How would I do part B?

Since you're not given the distance to the maid, you can't figure out exactly where the image is. However, if you call this distance d_o, can you describe where the image is with respect to the lens?

Also, what is the equation for the power of lens?

It's just the inverse of the focal length. Remember that by convention, focal length is positive for convex lenses and negative for concave ones.

 

[mukundpa]

can we use the formula for magnification of simple microscope in terms of focal length and the least distance of distinct vision?