Question

a object placed at a distance of 20 cm in front of a concave mirror and its focal length is 30 cm find the image distance​

Answer 1

Answer:

Here,

u= -30 cm

f= -20 cm

By using mirror formula,

1/v + 1/u = 1/f

1/v + 1/-30 = 1/-20

v= -60 cm

negative sign indicates that image is in front of the mirror

Therefore,

The distance between image and object = 60–30 = 30cm

Answer 2

Answer:

u=30cm

f=20cm

v=?

mirror formula

1/f= 1/v+1/u

for concave mirror f is in -ve

1/-20= 1/v-1/30

1/v= -1/20+1/30

1/v= -3+2/60

1/v= -1/60

v= -60

Explanation:-

hence image is formed at 60 cm at the same side of the mirror as that of the object

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