A girl is looking into her magnifying makeup mirror Behind h

A girl is looking into her magnifying makeup mirror. Behind her is a sunny window. She notices that, if she holds a piece of paper just right in front of the mirror, she can \"catch\" an image of the window on it. Given: The mirror is 2.79 m from the window which is 1.37 m tall. For the image to be in focus, the girl holds the paper 49.0 cm from the mirror. Find: (a) What is the focal length of the mirror? (b) How tall is the image? (c) Is the image right-side up or upside-down?

Solution

As Girl finds image of paper on the window.

that means image of paper formed by mirror is real and window is working as screen for this real image.

Object distance, p = 49 cm = 0.49 m

Image distance, q = 2.79 m

Applying 1/f = 1/p + 1/q

1/f = 1/0.49 + 1/2.79

f = 0.417 m Or 41.7 cm .............Ans

(B) magnification = - q / p = - 2.79 / 0.49 = - 5.69

so image will 5.69 times the size of paper.

(C) magnification is negative hence image will be upside-down (Inverted)