21, A converging lens of focal length 15 cm and a convergingmirror of focal length 20 cm are placed with theirprincipal axes coinciding. A point source S is placed onthe principal axis at a distance of 12 cm from the lensas shown in figure (18-W20). It is found that the finalbeam comes out parallel to the principal axis. Find theseparation between the mirror and the lens.12Ps'Figure 18-W20MMS1

21, A converging lens of focal length 15 cm and a convergingmirror of

1.	21, A converging lens of focal length 15 cm and a convergingmirror of focal length 20 cm are placed with theirprincipal axes coinciding. A point source S is placed onthe principal axis at a distance of 12 cm from the lensas shown in figure (18-W20). It is found that the finalbeam comes out parallel to the principal axis. Find theseparation between the mirror and the lens.12Ps'Figure 18-W20MMS1
Answer» 21, A converging lens of focal length 15 cm and a convergingmirror of focal length 20 cm are placed with theirprincipal axes coinciding. A point source S is placed onthe principal axis at a distance of 12 cm from the lensas shown in figure (18-W20). It is found that the finalbeam comes out parallel to the principal axis. Find theseparation between the mirror and the lens.12Ps'Figure 18-W20MMS1