Английский язык. Ч.3 (Units 9,10). Ильичева Н.А - 7 стр.

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    Reflecting surfaces do not have to be flat. The most common curved mirrors
are spherical, which means they form a section of a sphere. A spherical mirror
is called convex if the reflection takes place on the outer surface of the
spherical shape so that the centre of the mirror surface bulges out toward the
viewer (Fig. 4a). A mirror is called concave if the reflecting surface is on the
inner surface of the sphere so that the centre of the mirror sinks away from the
viewer (like a “cave”) (Fig. 4b). Concave mirrors are used as shaving or makeup
mirrors, and convex mirrors are sometimes used on cars and trucks (rearview
mirrors) and in shops (to watch for thieves), because they take in a wide field of
view. A concave mirror is commonly called a converging mirror because light
rays parallel to the principal axis converge and pass through the focal point. A
convex mirror is commonly called a diverging mirror. Parallel rays along the
principal axis are reflected so that they appear to diverge from the focal point.




               Figure 4a.                                  Figure 4b.
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   When light passes from one medium into another, part of the incident light is
reflected at the boundary. The remainder passes into the new medium. If a ray
of light is incident at an angle to the surface (other than perpendicular), the ray is
bent as it enters the new medium. This bending is called refraction. Fig. 5a
shows a ray passing from air into water. The angle Q1 is the angle of incidence
and Q2 is the angle of refraction. Notice that the ray bends toward the normal
when entering the water. This is always the case when the ray enters a medium
where the speed of light is less. If light travels from one medium into a second

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