Question

A concave mirror has a focal length of 9 cm. This mirror forms an image located 36 cm in front of the mirror. What is the magnification of the mirror? (Include the sign.)

Answer 1

f = 19 cm

q = 36 cm

using the lens equation

(1 / f) = (1 / p) + (1 / q)   => p = 12 cm

      M = - q / p = - 36 / 12 = - 3

Answer 2

1/f = 1/i + 1/o
where f = focal length
o = distance of object from lens
i = distance of image from lens

1/o = 1/9 - 1/36
o = 12cm

m = -36/12
m = -3, where the negative sign indicates the image is inverted

Answer 3

1/f = 1/i + 1/o
where f = focal length
o = distance of object from lens
i = distance of image from lens

1/o = 1/9 - 1/36
o = 12 cm

m = -36/12
m = -3, where the negative sign indicates the image is inverted