Question

A concave mirror has a focal length 20 cm . At what distance from the mirror should a 4 cm tall object be placed so that it forms an image at a distance of 30 cm from the mirror ? Also calculate the size of image formed


pls explain me what will be the sin convention of V...and why??/

Answer 1

f= -20cm and h of object = 4cm

v= -30cm

Mirror formula is 1/v+1/u=1/f

1/u= 1/-20-1/(-30)

=1/-20+1/30

= 3-2/60

=1/60

as we know u is always negative

so u= -60

magnification=-v/u

m=-(-30)/-60

m= 30/-60

m=-1/2

m=h of image /h of object

1/-2=h of image/4

4/-2=h of image

-2 =h of image

#answerwithquality #BAL