where should ab object be placed in front of concave mirror of focal lengthy 20cm so as to obtain real image two times magnified
where should ab object be placed in front of concave mirror of focal lengthy 20cm so as to obtain real image two times magnified
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Since, a real and magnified image is formed. Let object distance be –u, image distance be –v.
The magnification is given as, m = -v/u = -2 (negative sign appears with the number ‘2’ because the image is real)
Therefore, v = 2u
Now using mirror formula,
(-1/20) = (-1/v) + (-1/u)
=> 1/20 = 1/2u + 1/u
=> 1/20 = 3/2u
=> u = 30 cm (Objet distance = -u = -30 cm)
=> v = 60 cm (Image distance = -v = -60 cm)
So, the object must be placed at a distance 30 cm from the pole of the mirror.