Arun
Last Activity: 4 Years ago
Diverging lens =f= -20cm
converging mirror = f= 10cm
Let the object to placed at a distance x from the lens further away from the mirror.
For the concave lens (1st refraction)
u= - x
f= -20cm
1/v-1/u=1/f
1/v= - 1/20 -1/x
v= - (20x/x+20)
Virtual image formed due to first refraction forms as object for concave mirror.
for mirror :
1/f=1/u+1/v
u= -(5+20x/x+20)
= -(25x+100/ x+20)
f= -10cm
1/v= - 1/10 +x+20/25x +100
on solving we get
v= 50(x+4)/3x-20
Image will formed towards left of mirror
For second refraction in concave lens:
u= - [5- 50(x+4)/ 3x-20]
let v=+x
1/v-1/u=1/f
1/x+1/[5- 50(x+4)]/ 3x-20 = -1/20
25x²- 1400x-6000=0
x²-56x-240=0
(x-60)(x+4)=0
x= 60cm
object should be placed at a distance of 60cm from lens farther away from mirror so that final image is formed on itself
