Question

In a 35 mm single lens reflex camera (SLR) the distance from the lens to the film is varied in order to focus on objects at varying distances. Over what range must a lens of 45 mm focal length vary if the camera is to be able to focus on objects ranging in distance from infinity down to 1.4 m from the camera?

Answer 1

Answer:

range of movement is 1.49 mm

Explanation:

given data

focal length = 45 mm

distance = 1.4 m

distance from the lens = 35 mm

distance from infinity down = 1.4 m =

to find out

range of movement

solution

we will apply here lens equation that is

1/f = 1/p + 1/q

here f = 45 and p =  infinity to 1400 mm

we find here image distance that is q

1/45 = 0 + 1/q             ......1

q = 45 mm

and

1/45 = 1/1400 + 1/q     ......2

q = 46.49

so range of movement

that is 46.49 - 45

range of movement is 1.49 mm