An object is palced at a distance of 40 cm from the concave mirror of focal length18cm. What image is formed .

is it enlarged or diminished...expalin ur ans please !!An object is palced at a distance of 40 cm from the concave mirror of focal length18cm. What image is formed .
let the object distance=u= -40 cm


let the focal length =f= -18cm


[distances to the left are written with a negative sign]


let the image distance=v=?





BY the mirror formula,


1/f=1/v+1/u


=%26gt;1/f - 1/u=1/v


=%26gt;(1/-18) - (1/-40) =1/v


=%26gt;(1/40) - (1/18) =1/v


=%26gt;(9 - 20)/360 = 1/v


=%26gt; -360/11=v


=%26gt;v= -32.73 cm


the negative shows that the image is formed on the left hand side of the mirror and is real and inverted.





now,


magnification is -v/u


=33/-40


= -0.825


which shows that the image is 0.825 times the size of the object.


thus it is diminished.