An object 4.0 cm in size, is placed 25.0 cm in front of a concave mirror of focal length 15.0 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image ? Find the nature and the size of the image.

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. At what distance from the mirror should a screen be placed in order to obtain a sharp image ? Find the nature and the size of the image.
Answer» Solution :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) or v = - 37.5` cm The screen should be PLACED in front of the mirror at 37.5 cm. Image is real. Also, Magnification, `m = (h.)/(h) = - (v)/(u)` `RARR` Image-size, `h. = - (VH)/(u) = - ((-37.5 cm) (+4.0 cm))/((-25 cm))= - 6.0` cm