Question

An object 3cm high is placed 15cm in front of a convex mirror. If the image

distance is 5cm, calculate the focal length of the mirror. Find the height of the
image.​

Answer 1

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u = −12cm

f=+8cm

ho=+3cm

Using mirror formula,

v1+u1=f1

v1+−301=81

v1−301=81

v1=81+301

v1=603+2

v1=605=121

v=+12cm

Therefore, the image will be formed at a distance of 12cm behind the mirror.

m=um−v=−30m−12=+0.4

m=hohi

0.4=hohi

0.4=1hi

$\small \underline {\sf{ hi \ = \ + \ 0.4 \ cm}}$

Therefore, the image formed is diminished in size.

Answer 2

Answer:

u = −12cm

f=+8cm

ho=+3cm

Using mirror formula,

v1+u1=f1

v1+−301=81

v1−301=81

v1=81+301

v1=603+2

v1=605=121

v=+12cm

Therefore, the image will be formed at a distance of 12cm behind the mirror.

m=um−v=−30m−12=+0.4

m=hohi

0.4=hohi

0.4=1hi

\small \underline {\sf{ hi \ = \ + \ 0.4 \ cm}}

hi = + 0.4 cm

Therefore, the image formed is diminished in size.