1) surface energy = T.A

here A= 0.04

T= 5

there fore surface energy = 0.2

2) i think the answer is D

3),  answer is  3. just draw the figure and find out

OR brightness = n (lamda) D/d

here n=4

therefore =4(lamda)D/d.......................................<1>

and darkness = (n- 0.5) (lamda)D/d

here n=6

=5.5 (lamda)D/d................................................<2>

total dist = (4+5.5) (lamda)D/d.............................<adding 1 and 2>

total dist =9.5 times bandwidth

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