Question

What type of image is formed by a mirror if m = -0.4?

A. An image that is larger than the object and is in front of the mirror
B. An image that is smaller than the object and is behind the mirror
C. An image that is larger than the object and is behind the mirror
D. An image that is smaller than the object and is in front of the mirror

Answer 1

It is given to you that the magnification is equal to \(\color{blue}{\bf{-0.4}}\) .

For mirrors : \( m = \cfrac{I}{O}\) => I = Image Height and O = Object Height

As here, m < 1 , so, the Image Height is lesser than Object Height
Hence, i) Image is smaller than the Object

Also, \(m = - \cfrac{v}{u}\) ; v =Image distance, u = object distance

For mirrors, object distance is always negative. But, m is also negative. So, image distance will also be negative.

Thus, Image is formed in the front of the mirror.

Answer 2

if the number is less than 1 (m<1) then the image is smaller than the object but if m>1 then the image is greater than the object
the negative/positive sign indicates if the image is in the same orientation as the object

so how do you know? The formula for magnification is m= - di/do* so

*di means the distance from the mirror to the image while do is the distance from object to the mirror

di is + if the image is a real image and located on the object's side of the mirror.
di is - if the image is a virtual image and located behind the mirror.


In the end, if the fraction (di/do) is negative then the magnification will be positive but this question has a negative sign so then the fraction must be positive and therefore di will be + and so [from the above rules] the image is located on the object's side of the mirror.

Answer 3

Sorry my explanation is long but for your answer:

since usually the image is in front of the mirror then the image will be in front of the mirror and is smaller than the object

Answer 4

it's fine. thank u so much :)

Answer 5

no problem :D