A concave cosmetic mirror has a focal lengthof 34 cm . A 5.0-cm-long mascara bru

Question

A concave cosmetic mirror has a focal lengthof 34 cm . A 5.0-cm-long mascara brush is held upright 17 cm from the mirror.

Part A

Use ray tracing to determine the location of its image. How far is the image from the mirror? Input positive value if the image is on the same side from the mirror as an object and negative if the image is on the other side.

q=

Part B

What is the height of the image? Use ray tracing to determine.

h =

Part C

Is the image upright or inverted? Is it real or virtual?

Explanation / Answer

A)
from the given data

focal length of the morror, f = 34 cm

object distance, u = 17 cm

let v is the image distance.

Apply, 1/u + 1/v = 1/f

1/v = 1/f - 1/u

1/v = 1/34 - 1/17

v = -34 cm (negative sign indicates the image is virtual)

B) magnification, m = -v/u

= -(-34)/17

= 2

image height = m*object height

= 2*5

= 10 cm

C) The image is upright and virtual

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