A lantern gives an image of 3m square of a slide 7.62cm s...
A lantern gives an image of 3m square of a slide 7.62cm square on a screen. If the screen is 10m from the projection lens of the lantern, calculate the focal length of the lens
40.3cm
26.1cm
24.8cm
0.7cm
0.3cm
Correct answer is C
M = VHUH=3007.62
= 39.3
U = VM=100039.3 = 25.44
1f=IU+IV=I25.44=I1000=1025.4425440
f = 254401025.44=24.8
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