Consequently, the outgoing rays are reflected at many different angles and the image is disrupted. Reflection from such a rough surface is called diffuse reflection and appears matte.
In both cases the angle of incidence equals the angle of reflection at the point that the light ray strikes the surface. Light is also reflected when it is incident on a surface or interface between two different materials such as the surface between air and water, or glass and water.
The laws of reflection are obeyed at all interfaces. The amount of reflected light at the interface depends on the differences in refraction between the two adjoining materials. Allow cookies. Optics 4 Kids What is Optics? Reflection The Reflection of Light. This is controlled by the page's Image field. If you measure the angle of incidence and the angle of reflection against the normal, the angle of incidence is exactly the same as the angle of reflection.
With a flat mirror, it is easy to show that the angle of reflection is the same as the angle of incidence. Water is also a reflective surface. When the water in a lake or sea is very still, the reflection of the landscape is perfect, because the reflecting surface is very flat. However, if there are ripples or waves in the water, the reflection becomes distorted. This is because the reflecting surface is no longer flat and may have humps and troughs caused by the wind. It is possible to make mirrors that behave like humps or troughs, and because of the different way they reflect light, they can be very useful.
Concave mirrors are used in certain types of astronomical telescopes called reflecting telescopes. The mirrors condense lots of light from faint sources in space onto a much smaller viewing area and allow the viewer to see far away objects and events in space that would be invisible to the naked eye.
Light rays travel towards the mirror in a straight line and are reflected inwards to meet at a point called the focal point. Concave mirrors are useful for make-up mirrors because they can make things seem larger. This concave shape is also useful for car headlights and satellite dishes. Parallel rays of light strike the mirror and are reflected outwards. If imaginary lines are traced back, they appear to come from a focal point behind the mirror.
Convex mirrors are useful for shop security and rear-view mirrors on vehicles because they give a wider field of vision.
Some light is scattered in all directions when it hits very small particles such as gas molecules or much larger particles such as dust or droplets of water. Whenever we look into a mirror, or squint at sunlight glinting from a lake, we are seeing a reflection. When you look at this page, too, you are seeing light reflected from it. Large telescopes use reflection to form an image of stars and other astronomical objects. Figure 1. The angles are measured relative to the perpendicular to the surface at the point where the ray strikes the surface.
The law of reflection is illustrated in Figure 1, which also shows how the angles are measured relative to the perpendicular to the surface at the point where the light ray strikes.
We expect to see reflections from smooth surfaces, but Figure 2 illustrates how a rough surface reflects light. Since the light strikes different parts of the surface at different angles, it is reflected in many different directions, or diffused.
Diffused light is what allows us to see a sheet of paper from any angle, as illustrated in Figure 3. Many objects, such as people, clothing, leaves, and walls, have rough surfaces and can be seen from all sides. A mirror, on the other hand, has a smooth surface compared with the wavelength of light and reflects light at specific angles, as illustrated in Figure 4. When the moon reflects from a lake, as shown in Figure 5, a combination of these effects takes place.
Figure 2. Light is diffused when it reflects from a rough surface. Here many parallel rays are incident, but they are reflected at many different angles since the surface is rough. Figure 3. When a sheet of paper is illuminated with many parallel incident rays, it can be seen at many different angles, because its surface is rough and diffuses the light.
Figure 4.
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