When an object is placed 20cm from a concave mirror

Asked by admin @ 03/08/2021 in Math viewed by 315 People

When an object is placed 20cm from a concave mirror a real image magnified three times is formed find :

A)the focal length of the mirrorB)where must be the object be placed to give a virtual image three times the height of the object

Answered by admin @ 03/08/2021

Step-by-step explanation:

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....... :)

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