Question

Camera lenses are described in terms of

their focal length. A 50 mm lens has a focal
length of 50 mm. A camera is focused on an
object 13 m away using a 120 mm lens.
Locate the position of the image.
Answer in units of mm.

Answer 1

The position of the image from the camera lens is approximately 121.1 mm

Step-by-step explanation:

The given parameters of the lens are;

The specification of the camera lens = 120 mm

Therefore, the focal length of the camera lens, f = 120 mm = 0.12 m

The distance of the object from the camera,
`d_o` = 13 m

The lens equation for finding the position of the image is given as follows;

`(1)/(f) = (1)/(d_o) + (1)/(d_i)`

Where;

`d_i` = The position of the image from the camera lens

Therefore, by plugging in the known values, we have;

`(1)/(13) = (1)/(0.12) + (1)/(d_i)`

`(1)/(d_i) = (1)/(0.12) - (1)/(13) = (13 - 0.12)/(0.12 * 13) = (12.88)/(1.56) = (322)/(39)`

`\therefore d_i = (39)/(322) \approx 0.1211`

The position of the image from the camera lens,
`d_i` = 0.1211 m = 121.1 mm