Question

6. An object 4 cm in size is placed at a distance of 25 cm from a concave mirror of focal
length 15 cm. Find the position, nature and height of the image.​

Answer 1

u=? , v=-25. , f=-15 , h=4

1/f=1/v+1/u

1/-15=1/-25+1/u

1/-15+1/25=1/u

-5+3/75=1/u

-2/75=1/u

u = 75/-2 = -37.5

m=h'/h=-v/u

h'/4=-(-25)/-37.5

h'=-25×4/-37.5

h'=2.66

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Answer 2

Answer:

37.5 cm

Explanation:

Given,

focal length f=15cm

object distance,u=25cm

object height,h=4cm

from mirror formula,

1/f=1/v+1/u

1/-15=1/-25+1/v

1/v=1/-15+1/25

v= -37.5cm

magnification,m=-v/u =hi/ho

=m= ( -37.5)/-25 =hi/4

hi= -37.5*4/25

hi=-6cm

To get a sharp image,v=37.5cm

The image is real,inverted and magnified