Mirages occur when air?s refractive index varies with position as a result of uneven heating. Under such conditions, light undergoes refraction continually and thus follows a curved path. Other examples where a varying refractive index is important include the eye?s lens and Earth?s ionosphere, an electrically conductive layer in the upper atmosphere, where the refractive index for radio waves varies with altitude.

Figure 30.25a depicts light?s path over a hot road, producing a mirage. From the path shown, you can conclude that the air?s refractive indexa. increases from left to right.b. increases from right to left.c. increases upward.d. increases downward.

Transcribed Image Text:

Light path ... C B A D (a) Ionosphere "Radio-wave paths A Earth B (b)