An object 4.0 cm in size, is placed 25.0 cm in front of a concave mirror of focal length 15.0 cm.(i) At what distance from the mirror should a screen be placed in order to obtain a sharp image.(ii) Find the size of the image.(iii) Draw a ray diagram to show the formation of image in this case.

An object 4.0 cm in size, is placed 25.0 cm in front of a concave mirr

1.	An object 4.0 cm in size, is placed 25.0 cm in front of a concave mirror of focal length 15.0 cm.(i) At what distance from the mirror should a screen be placed in order to obtain a sharp image.(ii) Find the size of the image.(iii) Draw a ray diagram to show the formation of image in this case.
Answer» Solution :(i) Object-size, H=+4.0 cm, Object-distance, u = -25.0 cm, Focal length, f = -15.0 cm, From mirror formula, `1/v=1/f-1/u=(1)/(-15)-(1)/(-25)=-(1)/(15)+(1)/(25)` or`1/v=(-5+3)/(75)=(-2)/(75)` orv=-37.5 cm So the screen should be placed in front of the mirror at 37.5 cm (II)Magnification, m=`(h.)/(h)` = `-v/u` `implies` Image-size,h. = `-(vh)/(u)`=`-((-37.5)(+4.0))/((-25))` = -6.0 cm So height of image is 6.0 cm and the image is an invested image. (iii) Ray diagram SHOWING the formation of image is given below :