Electrodynamics and Optics

Homework 3

1. Apertures

An aperture is placed in front of a positive lens. An object in front of the aperture forms a real image on the other side of the lens. What happens to the image as the aperture is gradually closed?

2. Waveguides

If you had a tapered fiber like the one shown in the figure, could you concentrate all the light in the wide section into the narrow section? Why or why not? Hint: What about the various modes?

light

3. You have two identical plano-convex lenses, as shown below. You coat the opposite sides of them with aluminum and shine light into the uncoated side. What is the ratio of the focal lengths of the reflected light?

light light

4. You have the following image and object from a lens system

Draw a ray diagram and show that the intermediate lens where the vertical line is must be a positive lens.