Question

An object of size 7 cm is placed at 27 cm in front of a
concave mirror of focal length 18 cm. The distance of
image and size of the image -
A.54 cm, 14 cm
B.-54 cm, -14 cm
C.-54 m, 14 m
D.54 m, -14 m​

Answer 1

$\huge\boxed{Answer}$

For a concave mirror -

u = -27 cm , f = - 18 cm

From mirror formula :-

1/f = 1/v + 1/u

1/(-18) = 1/v + 1/(-27)

-1/18 = 1/v - 1/27

1/v = -1/18 + 1/27

1/v = (-3 + 2)/54

1/v = -1/54

v = -54 cm

Now ,

h2/h1 = -v/u

h2/7 = 54/(-27)

h2/7 = -2

h2 = -14 cm

Result :-

position of reflection = -54 cm

Size of reflection = -14 cm

Answer 2

$\huge{\bold{\star{\fcolorbox{black}{red}{Question}}}}$

An object of size 7 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. The distance of image and size of the image -

A.54 cm, 14 cm

B.-54 cm, -14 cm

C.-54 m, 14 m

D.54 m, -14 m

$\huge{\bold{\star{\fcolorbox{black}{red}{Answer}}}}$

For a concave mirror -

u = -27 cm , f = - 18 cm

From mirror formula :-

1/f = 1/v + 1/u

1/(-18) = 1/v + 1/(-27)

-1/18 = 1/v - 1/27

1/v = -1/18 + 1/27

1/v = (-3 + 2)/54

1/v = -1/54

v = -54 cm

Now ,

h2/h1 = -v/u

h2/7 = 54/(-27)

h2/7 = -2

h2 = -14 cm

Result :-

position of reflection = -54 cm

Size of reflection = -14 cm