Rohit placed a pencil perpendicular to principal axis in front of a converging
mirror of focal length 30 cm. The image formed is twice the size of the pencil.
Calculate the distance of the object from the mirror.

45 cm ( in my opinion)‍♀️

Explanation:

( Using the mirror formula)

1/ u + 1/v = 1/f

( introducing magnification; m into the formula )

u( 1/u  + 1/v ) =u×1/f

1 + u/v =u/f

( But u/v =1 ÷v/u= 1/m)

1 +1/m =u/f

1 + 1/2 =u/30

2+1= u/15

3=u/15

3×15=u

45 cm=u

answer; how far out of place which the object finished relative to the starting location;

d. platinum would have the greatest temperature increase because it has the lowest specific heat.