What kind of mirror (concave, convex, or plane) do you think dental care workers use to examine patients' teeth and gums for disease? Explain your choice.

As the footnote on above page indicates, the separation, $\Delta x$, between two adjacent bright areas or fringes in the double slit interference pattern is determined by the distance, $a$, between the slits, the distance, $S$, between the plane of the slits and the screen on which the pattern is projected, and the wavelength, $\lambda$, of light used in the experiment. Specifically, the relationship among these variables is given by:

$$\Delta x=\left(\frac{S}{a}\right) \lambda .$$

Based on this equation, for a given slit spacing and screen distance, for which color of light, red or blue, will the fringe spacing be greater? For a given slit spacing and wavelength, if the screen distance, $S$, is increased, what happens to the fringe spacing? If the separation between the slits is decreased, for a given value of $\lambda$ and $S$, how will $\Delta x$ change? Suppose that a beam of red light from a He-Ne laser $(\lambda=633 \mathrm{~nm})$ strikes a screen containing two narrow slits separated by $0.200 \mathrm{~mm}$. The fringe pattern is projected on a white screen located $1.00 \mathrm{~m}$ away. Find the distance in millimeters between adjacent bright areas near the center of the interference pattern that develops. As mentioned in the text, the relationship given above could be used to calculate the wavelength of light in an experiment in which the other three quantities are measured.

A heat lamp is designed to keep food and other things warm. Would it also make a good tanning lamp? Why or why not?

When a piece of plastic tape coated with iron oxide that is magnetized more in some parts than others is moved past a small coil of wire, what happens in the coil? What is a practical application of this?

List several examples of the use or application of Fresnel lenses in today's world.

Distinguish between specular reflection and diffuse reflection.

Two plane mirrors are hinged along one edge and set at right angles to one another as shown in Figure mentioned. A light ray enters the system, striking mirror 1 with an angle of incidence of $45^{\circ}$. Draw a diagram showing the direction in which the ray will exit the system. This device is called a corner reflector and is the basis for the design of bicycle reflectors and some highway signs.

What do you see if you hold out your right hand in front of an aeroplane mirror? (Be cautious now. Describe the image carefully.) If you’re having trouble, place a tube of toothpaste or other object with writing on it in front of the mirror. Now what can you say? (The process you’re witnessing is called inversion and is one of the common characteristics of plane mirrors.)

In a double-slit interference experiment, a special lamp emitting yellow light from heated sodium atoms is used to produce an interference pattern on a screen located $1.50$ m from a pair of slits separated by $0.10 \mathrm{~mm}$. If the distance between adjacent bright regions in the resulting pattern is $8.84 \mathrm{~mm}$, what is the wavelength of the sodium light?

If the wavelength of light is doubled, by what fraction does the amount of the light scattered by Earth's atmosphere change? Is the amount of light scattered at the new wavelength larger or smaller than the amount of light scattered at the old wavelength?

Consider Figure mentioned below. At which of the lettered positions would an observer be able to see the image of the dot in the mirror?

Compute the approximate ratio of the amount of blue light in scattered sky light to the amount of orange.

Light traveling along direction $\mathrm{SO}$ strikes the surface of a plane mirror. Which of the paths $O P, O Q, O R$, or $U I$ best describes the path of the light reflected from the mirror? Defend your choice by appealing to the appropriate law(s) of optics.

If the mirror described in the previous problem is used to form an image of the same object now located $16 \mathrm{~cm}$ in front of the mirror, what would the new image position be? Assuming that the magnification equations developed for lenses also apply to mirrors, describe the image thus formed.