Regular reflection definition physics8/31/2023 ![]() Since the light rays do not actually pass through the focus (or foci) of a concave lens, therefore, a concave lens has a virtual focus. ![]() The two foci of a lens are at equal distances from the optical centre, one an either side of the lens. However a concave lens has two spherical surfaces and hence it has two principal foci or two focal points which are usually denoted by the letters ‘F1’ and ‘F2’ and are known as the first principal focus ‘F1’ and the second principal focus ‘F2’. It is usually represented by the letter ‘F’. The principal focus of a concave lens is a point on its principal axis from which light rays parallel to the principal axis, appear to diverge after refraction by the lens. Since there are two centres of curvature, we may represent them as C1 and C2.Īn imaginary straight line passing through the two centres of curvature of a lens is called its principal axis. The centre of curvature of a lens is usually represented by the letter C. The centres of these spheres are called centres of curvature of the lens. Each of these surfaces form a part of a sphere. In the figure (a), (b) ‘AB’ is the diameter of the circular outline of the lens which represents aperture of the lens or we can say that aperture is the actual refracting surface of the lens.Ī lens, either a convex lens or concave lens, has two spherical surfaces. The effective diameter of the circular outline at a spherical lens is called its aperture. A ray of light passing through the optical centre at a lens goes undeviated. It is usually represented by the letter O. The centre point of a lens is known as its optical centre. SOME IMPORTANT TERMS ASSOCIATED WITH SPHERICAL LENSES The angle between the reflected ray and normal to the surface is called the angle of reflection. ![]() The angle of reflection is the angle made by the reflected ray with the normal at the point of incidence. In this case only the surface is visible and not the image. Laws of reflection are not valid in irregular reflection. Such a reflection is known as irregular reflection or diffused reflection or scattering of light. When the reflecting surface is rough, the parallel rays falling on it are reflected in different directions as shown in the figure. It is the regular reflection that makes the object visible. The laws of reflection are valid only in regular reflection. Then it is known as a regular reflection. the reflected light goes in one particular direction as shown in the figure. mirror, the parallel rays falling on it are reflected parallel to one another i.e. Do the same for rough surfaces and observe the changes in the reflection pattern of light.When the reflecting surface is smooth and well polished, e.g. Observe that when light is reflected from a smooth mirror then it is in a definite direction or in all directions. Take a smooth mirror and a rough wood and observe regular and irregular reflection of sunlight. Note: We can observe both regular and irregular reflection practically. In irregular reflection, light reflected from a rough surface in all directions and not in a definite direction. In regular reflection, light reflected from a smooth surface in a definite direction. Reflection from a rough and uneven surface for example wood, leaf of tree, piece of paper etc gives irregular reflection. Reflection from smooth highly polished surface for example mirror, surface of silver gives regular reflection. If all the parallel rays which are reflected from a plane surface are parallel then that reflection of incident rays is known as regular reflection. If all the parallel rays which are reflected from a plane surface are not parallel then that reflection of incident rays is known as irregular reflection. ![]() Difference between regular and irregular reflection is as follows.
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