Question

the concave mirror of radius of curvature 20 cm is placed at a distance of 35 cm from a screen calculate the distance of an object which may be placed in order to get its real image on the screen

Answer 1

gn,

R= -20 cm
f = R/2
=20/2
f=-10cm
1/f=1/v+1/u
-1/10=-1/35+1/u
u=- 14 cm

Answer 2

f=r/2
f=20/2
f=10
u=-35
put the value mirror formula
1/v+1/u=1/f
1/v=1/f-1/u
=1/-10-1/-35
= LCM=70
=-7+2/70
=-5/70
v=70/-5
v=-14