A photographic camera with a lens of focal length 5 cm is used for capturing images. The vertical length of the film used is 24 mm in which image of a 1.68 m tall man is to be captured. Find the minimum distance (in m ) of the man from the lens such that his complete image can be obtained.

Question

A photographic camera with a lens of focal length 5 cm is used for capturing images. The vertical length of the film used is 24 mm in which image of a 1.68 m tall man is to be captured. Find the minimum distance (in m ) of the man from the lens such that his complete image can be obtained. (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

The lens of a camera is convex and the image is inverted m=(hi/ho)=-(24 m m/1.68 m)=-(1/70) m=(f/f + u)=-(1/70) 70f=-f-u -u=71f=355cm=3.55m

Q. A photographic camera with a lens of focal length 5cm is used for capturing images. The vertical length of the film used is 24mm in which image of a 1.68m tall man is to be captured. Find the minimum distance (in m ) of the man from the lens such that his complete image can be obtained.

The lens of a camera is convex and the image is inverted m=ho​hi​​=−1.68m24mm​=−701​ m=f+uf​=−701​ 70f=−f−u −u=71f=355cm=3.55m

The lens of a camera is convex and the image is inverted
$m = \frac{h _{i}}{h _{o}} = - \frac{24 mm}{1.68 m} = - \frac{1}{70}$
$m = \frac{f}{f + u} = - \frac{1}{70}$
$70 f = - f - u$
$- u = 71 f = 355 c m = 3.55 m$