When an object is placed 20cm from a concave mirror,a real image magnified three times is formed . Find the focal length of the mirror.Where must the ovject be placed to give a virtual image three times the hight of the object?
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When an object is placed 20cm from a concave mirror,a real image magnified three times is formed . Find the focal length of the mirror.Where must the ovject be placed to give a virtual image three times the hight of the object?
Answer
magnification m = -3
U = -20 cm
m = -v/u
-3 = -v/( -20) by calculating this step we will get answer as
V = -60cm
So , the image is located 60 cm Infront of the mirror
☣MIRROR FORMULA☣
1/v +1/u =1/f
1/(-60) +1/(-20) =1/(f )
By calculating we will get the answer as
F = -15 cm
(2) m =h2 /h1
m = -v/u =3
V = -3u
☣MIRROR FORMULA☣
Applying again
1/v + 1/u = 1/f
1/(-3u) + 1/u =1/(-15)
By calculating we will get the answer as -10cm
That is u = -10cm //.
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