a biconvex lens of the focal length 15cm is in front of a plane mirror the distance between the length and the breadth is 10 centimetre a small object is kept at the distance of 30 cm from the lens then the final image is
a virtual and real a distance of 16 cm from the mirror
b real and a distance of 16 cm from the mirror
c virtual and a distance of 20 cm from the mirror
d real at a distance of 20 cm from the mirror
Answers
Answer:
Explanation:
We get the image distance due to the lens using lens formula,
v
1
−
u
1
=
f
1
or
v
1
=
15
1
−
30
1
or
v=30cm in front of the convex mirror, which means 20cm behind the mirror. Assuming mirror to reflect from both the sides and this image will act as virtual object for mirror and second image, I
2
will be formed at 20 cm in front of mirror. That is 10 cm in front of lens.
Understanding the convention used while taking +ve and -ve sign for image and object distance, the direction along which ray of light travels is taken as +ve.
So, here, the ray of light is coming from behind the mirror towards lens, for the second image, I
2
with respect to lens,
u=+10cm;f=15cm
So, applying lens formula,
v
1
−
u
1
=
f
1
or
v
1
−
10
1
=
15
1
or
v=6cm from lens (in front of lens)
So this image is at a distance of 16 (10 + 6) cm in front of mirror.
solution