An object 2 cm in size is placed 30cm in front of a concave mirror of focal length 15cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? What will be the nature and the size of the image formed? Draw a ray diagram to show the formation of the image in this case.
According to the question;
Object distance (u) = -30cm;
Focal length (f) = -15cm;
Image distance = v;
By mirror formula;
⇒ 
⇒ v = 30cm.
Thus, screen should be placed 30cm in front of the mirror (Centre of curvature) to obtain the real image.
Height of object h1= 2cm;
Magnification = 
= 
Putting values of v and u
Magnification = 
⇒ 
⇒ 
Height of image is 2 cm.
Negative sign means image is inverted.
Thus real, inverted image of size same as that of object is formed.
Diagram below shows the image formation.
