Question

real image formed by concave mirror is 4 times its object image if object is shifted 3 CM away from the mirror then images three times the object find focal length​

Answer 1

Answer:36 cm

Explanation:

m=−vu=−4  

⟹v= 4u

−v′u+3=−3  

⟹v'=3u+9

1v+1u=1v′+1u+3=1f

⟹14u+1u=13u+9+1u+3  

⟹54u=43u+9

⟹15u+45=16u

⟹u=45

f=45×u=36cm