The image of an object placed at 60 cm in front of a lens is obtained on a screen at a distance of 120 cm from it. Find the focal length of lens. What would be the height of the image if object is 5 cm high .draw a ray diagram.
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Answers
Answered by
1
Object distance u = -60 cm
Image distance v = +120 cm
Lens formula, 1/f = 1/v - 1/u
1/f = 1/120 - ( -1/60 ) = 1/120 + 1/60 = 3/120 = 40
f = +40 cm
H(image) / H(object) = v/u
Hi = -120/60 X 5 = -10 cm
Answered by
2
Explanation:
u(obj.distance)=60cm
v(image distance)=120cm
f=?
using lens formula,
1/v-1/u=1/f
=1/120-1/(-60)=1/-f. (since u and f would -ve in this case )
=1+2/120=1/-f
f=-120/3
therefore f= -40 cm
we know that,
hi/ho=v/u
h(i)/5=120/-60
h(i)=-10 cm therefore height of image is 10cm
and -ve sign represent it is inverted..
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