Question

To solve a problem using lens formula, if object distance, focal length and height of the object is given, the height of the image can be calculated.

• A. Always false
• B. Always true
• C. Sometimes true
• D. Sometimes false

Answer 1

The correct option is B

Always true

We have total five variables:
u (object distance)
v (image distance)
f (focal length)
$h_0$ (height of the object) and
$h_i$ (height of the image)

We have two equations:
$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}\left(lensformula\right)$ $\frac{h_i}{h_0}=\frac{v}{u}\left(magnificationformula\right)$
So, if three of the quantities are known; the other two can be calculated.