A diverging lens has a focal length of 20cm, at what distance should an object of height 4cm from the optical centre of lens be placed so that it's image is formed 10cm away from the lens.Find the size of the image and draw the ray diagram to show the formation of the image
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f=-20cm
h=4cm
v=-10cm
u=?
h'=?
1/v - 1/u =1/f
1/-10 - 1/u = 1/-20
-1/10 + 1/20=1/u
-2/20+1/20=1/u
-1/20 = 1/u
u = -20cm ✓ Position of object from lens is 20cm
m=v/u
=(-10)/(-20)
= 1/2
h'/h=m
h'/4=1/2
h'=2cm ✓ Size of image is 2cm
h=4cm
v=-10cm
u=?
h'=?
1/v - 1/u =1/f
1/-10 - 1/u = 1/-20
-1/10 + 1/20=1/u
-2/20+1/20=1/u
-1/20 = 1/u
u = -20cm ✓ Position of object from lens is 20cm
m=v/u
=(-10)/(-20)
= 1/2
h'/h=m
h'/4=1/2
h'=2cm ✓ Size of image is 2cm
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