someone do it plz
A tube of length 30 cm has its inner lateral surface blackened.Two lenses of focal length 10 cm and 20 cm are fixed at the end of the tube.for the same beam intencities on the screen are I1 and I2 for arrangement 1 and 2 respectively.then I1/I2=
arrengement 1 arrengement 2
(1)1
(2)16
(3)1/16
(4)0.25
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UP 0 DOWN 0 0 2