Question

When an object is placed 20 cm from a concave mirror, a real image magnified three times is formed. Where must the object be placed to give a virtual image three times the height of the object?
Please give clarified answer I will mark as brainliest.

Answer 1

a)
Magnification, m=-3 (Image is real)
Object distance, u=-20cm
Magnification, m=-v/u
-3=- v/(-20)
v=-60 cm
Thus the image is located at a distance of 60cm in front of the mirror.
Now using the mirror formula,
1/v +1/u=1/f
1/(-60) + 1/(-20)=1/f
f=-15 cm
(b)
m=h2 /h1=- v/u=3
v=-3u
Using mirror formula,
1/(-3u) +1/u=1/-15
u=-10 cm
 

Answer 2

DEAR STUDENT

GIVEN

Magnification, m= -3

Object distance, u= -20cm

USING MAGNIFICATION FORMULA

m = -v/u

-3 = - v/ -20

v = - 60 cm

distance of the image from the mirror is - 60

USING MIRROR FORMULA

1/f = 1/v +1/u

1/f = 1/ -60 + 1/ -20

f = -15 cm

the focal length of the mirror is -15

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to find the distance of the object from the mirror

USING MAGNIFICATION FORMULA

m = h (height of image) / h (height of object)

m = -v/u

as per question ''three times the height of the object''

v= -3u

USING MIRROR FORMULA

1/ -3u + 1/u = 1/-15

u= -10 cm

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hope it helped....... :)