# If you look at yourself in a shiny Christmas tree ball with a diameter of 10.5 cm when your face...

## Question:

If you look at yourself in a shiny Christmas tree ball with a diameter of 10.5 cm when your face is 35.0 cm away from it,

(a) where is your image?

(b) Is it real or virtual?

(c) Is it upright or inverted?

## Mirror Formula:

The formula that provides the relation between the object distance, image distance and the focal length of the mirror is known as mirror formula. According to this formula, the sum of the reciprocal of the image and object distance is equal to the reciprocal of the focal length of the mirror.

## Answer and Explanation:

**Given Data:**

- Object distance {eq}(u) = 35 \rm \ cm {/eq}

- Diameter of the mirror {eq}(d) = 10.5 \rm \ cm {/eq}

- focal length of the mirror {eq}f = \dfrac{-d}{4} \\ f = \dfrac{-10.5}{4} \\ f = -2.625 \ cm {/eq}

**(a)**

Now, apply the mirror formula

{eq}\dfrac{1}{u} + \dfrac{1}{v} = \dfrac{1}{f} \\ \dfrac{1}{35} +\dfrac{1}{v} = \dfrac{-1}{2.625} \\ v = -2.442 \ cm {/eq}

where

- v is the image distance

**(b)**

Since the image distance is negative, therfore image would be virtual.

**(c)**

It would be upright.

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from Physics 101: Help and Review

Chapter 14 / Lesson 17