Question

The focal length of a camera lens is 20 cm from the film must be the lens set in order to photograph an object located at a distance of 100 cm from the lens.​

Answer 1

Appropriate question:

The focal length of a camera lens is 20 cm. Find how far away from the film must be the lens set in order to photograph an object located at a distance of 100 cm from the lens.

Given information to us:

• Focal length of camera = 20 cm
• Distance = 100 cm

Need to be solved?

• We have to find the how far away from the film must be the lens set in order to photograph an object located at a distance of 100 cm from the lens.

Step by step explaination:

Here we have been given the values of focal length and distance from the object. We have to calculate the distance of image. That would be calculated as follows:

We would be using the formula of lens formula:

• 1/v - 1/u = 1/f

Here v is distance of image,

u is distance of object and,

f is focal length between them.

Using the given formula of lens by changing the sides inorder to calculate the distance of image.

Now,

1/v = 1/u + 1/f

Substituting values.

1/v = 1/-100 + 1/20

Adding and solving further.

1/v = 1/25

v = 25

Answer:

Hence , lens should be setted at a distance of 25 cm.