Question

An object 4.0cm in size is placed at 25.0cmin front of a concave mirror of focal length 15.0cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Find the nature and size of the mirror

Answer 1

h = 4.0cm

u = -25.0cm

f = -15.0cm

MIRROR FORMULA : 1/v + 1/u = 1/f

1/v + 1/-25.0= 1/-15.0

1/v =1/-15.0 + 1/25.0

1/v = -5/75 + 3/75

1/v = -2/75

v = -75/2cm

4/h1 = - - 75/-50

-75h1 =50 x 4

-75h1 = 200

h1 = -200/75 cm

Answer 2

1/v+1/u=1/f
1/u=1/f-1/v
1/u=1/15-(1/-25)
1/u=1/15+1/25
1/u=5+3/75
1/u=8/75
u=75/8
u=9.3cm

m=h'/h=-v/u
h'/4=25/9.3
h'=25×4/9.3
h'=1000/93
h'=107.5cm