you are given three lenses L1, L2 ,L3 each of focal length 10 cm.An object is kept at 15 cm in front of L1 . The final real image is formed at the focus 'I' of L3 .Find the seperations between L1 , L2 and L3
Answers
Answered by
89
f1=f2=f3=10cm
1/f1= 1/v1-1/u1
1/v1=1/f1 +1/u1
= 1/10-1/15
= 1/30
v1=30cm
now image by L3 is formed at focus.
thus object for L3 is placed at infinity.
and hence image firmed by L2 is at infinity.
thus u2= 10cm
object for L2 is placed. at 10cm left from L2 which is 30cm right from L1 as image of L1 is formed at30cm right of L1
so X1 = distance between L1 and L2
=v1+ u2=30+10= 40cm
Therefore L2 make s image at infinity , any distance between L2 and L3 will make the object for L3 as infinity.
L2 and L3 = any length
1/f1= 1/v1-1/u1
1/v1=1/f1 +1/u1
= 1/10-1/15
= 1/30
v1=30cm
now image by L3 is formed at focus.
thus object for L3 is placed at infinity.
and hence image firmed by L2 is at infinity.
thus u2= 10cm
object for L2 is placed. at 10cm left from L2 which is 30cm right from L1 as image of L1 is formed at30cm right of L1
so X1 = distance between L1 and L2
=v1+ u2=30+10= 40cm
Therefore L2 make s image at infinity , any distance between L2 and L3 will make the object for L3 as infinity.
L2 and L3 = any length
Similar questions