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.

The observer in Fig. 30.25a sees a shimmering mirage that looks like water but actually results from sky light following the curved path. To the observer, the mirage appears to be ata. point A.b. point B.c. point C.d. point D.

Transcribed Image Text:

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