Question

A 30cm tall pug is standing 120cm in front of a convex lens that creates an image 30 cm on the opposite side of the lens. What is the focal length of the lens, and the magnification of the pug?

Answer 1

Answer:

The focal length of the lens = 24 cm

The magnification of the pug = 0.25

Step-by-step explanation:

The height of the pug = 30 cm

The pug's distance from the convex lens, u = 120 cm

The image distance from the convex lens, v = 30 cm

Calculate the focal length using the equation below

`(1)/(f)=(1)/(u)+(1)/(v)`

Substitute u = 120 cm, v = 30 cm, and solve for f

`\begin{gathered} (1)/(f)=(1)/(120)+(1)/(30) \\ (1)/(f)=(1+4)/(120) \\ (1)/(f)=(5)/(120) \\ f=(120)/(5) \\ f=24\text{ cm} \end{gathered}`

The focal length of the lens = 24 cm

The magnification of the pug = v/u

Magnification = 30/120

Magnification = 0.25

The magnification of the pug = 0.25