8/17/2019 Ansd
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Question: A point object is kept between a plane mirror and a concave mirror facing each other.The
distance between the mirrors is 22.5cm.Plane mirror is placed perpendicular to the
principal axis of the concave mirror.The radius of curvature of the concave mirror is
20cm.hat should be the distance of the object from the concave mirror so that after two
successive reflections the final image is formed on the object itself.
Answer:
!
! ! !
" "!0v x + =
!
!0
!0 "
x v
x
=
#irst image will form at $!
This!
v
will come in negative so adding the negative sign makes the image distance refer
onl% to magnitude
!0 " 22.5 22.5 "
!0 "
x x
x
= +
!0 x & ' x " (5) '!0 " x )
0 & " (50 " x 2 * (5 x
x 2 " (5u * (50 & 0
Solving
2(5 (5 " ( (50
2 x
± ×=
(5 !5
2 x
±=
& +0 cm and !5 cm
,orrect answer is !5 cm as +0 cm is be%ond plane mirror.
8/17/2019 Ansd
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