(A) (i) The point of the principle axis from where all the incident rays appear to diverge from behind the mirror, is called principle focus of the diverging mirror.
(ii) The distance between the pole of the mirror and its principal focus is called focal length.(B) Object height, O=+10‌cm
Focal length, f=+15‌cm
Object distance, u=−25‌cm
Image distance, v= ?
Image height, I= ?
Using lens formula, ‌

1

f

=‌

1

v

−‌

1

u

‌

1

15

=‌

1

v

−‌

1

(−25)

Or,
‌

1

v

=‌

1

15

−‌

1

25

‌

1

v

=‌

2

75

v=‌

75

2

Also, ‌‌‌

−v

u

=‌

I

O

Hence, ‌

− 75 2

−25

=‌

I

10

I=(−1.5)×10=15‌cm
Height of image is 15‌cm, inverted.