Question

At what distance from a concave mirror of focal length 10cm should an object 2cm long be placed in orders to get an erect image 6cm tall?​

Answer 1

Answer: 6.66....cm from pole

Explanation:

M(magnification) =-h'/h(image height/object height)

M=-6/2=-3

Also M=f/f-u

+ 3=10/10-u (f= -ve,concave)

- 3(-10-u)=-10

30+3u=10

20=-3u

-20/3=u

u=-6.66....cm

Answer 2

Answer:

6.66....cm from pole

Explanation:

M(magnification) =-h'/h(image height/object height)

M=-6/2=-3

Also M=f/f-u

+ 3=10/10-u (f= -ve,concave)

- 3(-10-u)=-10

30+3u=10

20=-3u

-20/3=u

u=-6.66....cm