UNDERSTANDING REFLECTION OF LIGHT

LAW OF REFLECTION

a.  LAW (1) : the incident ray , the normal and the reflected ray at the point of incidence . all lie on the same plane.

b.  LAW (2) : the angle of incidence , i , is equal to the angle of reflection , r .DIAGRAM

APPLICATIONS OF REFLECTION OF LIGHT

(I)PLANE MIRROR

1. We usually look at ourselves in a plane mirror to make ourselves presentable.

2. Plane mirrors are fixed in barber shops to enable customers to see whether they are having a satisfactory hair-cut. Many shops are fixed with plane mirrors which can make shops look wider, besides being decorative.

3. Plane mirrors have been used extensively in optical instruments such as periscopes, overhead projectors (OHP) and cameras. Electric meters such as the ammeter and the voltmeter have a plane mirror under the pointer to help users obtain accurate readings. The correct position for the eye to take a correct reading with no parallax error is where the eye cannot see the image of the pointer.

4. a plane mirror fixed at one and of a ,metal rod is a very useful instrument for a dentist. By placing the plane mirror at the back of the teeth, a dentist can look at teeth through their image in the mirror.

(II)CONCAVE MIRRORS

1.  Concave mirrors used as shaving mirrors or make-up mirrors enable a person standing close to the mirrors to see their own enlarged, upright and virtual image.

2.  Concave mirrors are usually used as light reflectors in torchlights, car headlights and various searchlights (spotlights) to produce parallel beams of light.

3.  In the reflecting telescope invented by Newton , a concave mirror is used to focus parallel rays of light from a distant star. The Hale Telescope which is the largest reflecting telescope at the Mount Palomar observatory in California has a concave mirror with a diameter of about 5 m. such a large mirror can collect enough light energy to enable very distant stars and nebulae to be seen or photographed.

(ii(III) CONVEX MIRRORS

1.  Car rearview mirrors making use of plane mirrors are limited to only providing a narrow field of view.

2.  Convex mirrors are preferred as car rearview mirrors because they can provide a wider field of view than plane mirrors.

 For the same reason, large convex mirrors are often placed at sharp road corners or dangerous bends to enable the motorist to see the oncoming traffic