Answer to Question #157241 in Physics for kate

Question

Lens Equation

Solve the following problems.

3. A diverging lens formed an image that is 20.0 cm in front of it. If the focal length

of the lens is 25 cm, where is the object placed?

4. An object 20 cm high is placed 50 cm from a concave lens whose focal length is

20 cm.

a. Where is the image located?

b. What is the size of the image?

c. Construct a ray diagram.

d. Describe the image formed.

Answer 1

3.

$\frac{1}{a}-\frac{1}{b}=-\frac{1}{f}\to\frac{1}{a}-\frac{1}{0.2}=-\frac{1}{0.25}$

$\frac{1}{a}=1\to a=1(m)$ .Answer

4.

a. $\frac{1}{a}-\frac{1}{b}=-\frac{1}{f}\to \frac{1}{0.5}-\frac{1}{b}=-\frac{1}{0.2}\to$

$b=0.14(m)$ . Answer

b. $\beta=b/a=0.14/0.5\approx0.29$ .Answer

c.

d. The image is virtual, reduced and direct. Answer