CBSE Class 8 Answered

how to make ray diagrams

Asked by ojasanchi15 | 23 Feb, 2018, 09:21: AM

Expert Answer

One of the important property of light is rectilinear propagation. It means light travels in straight line. Ray daigrams are drawn based on this principle.

Ray diagrams are drawn to illustrate the phenomenon like reflection of light, refraction of light.

So when we want to draw ray diagram we have some principle behind this phenomena and rules for drawing ray diagrams are based on this principle.

For example, as per laws of reflection, angle of reflection is equal to angle of incidence and incident ray, normal and reflected ray are in same plane.

So when we need to draw the ray diagram to describe this, we need to draw a straight line from a point to the point of incidence of light, let it be on a mirror's reflecting surface. if we draw a normal at the point of incidence we get angle of incidence of light. Hence from the same point of incidence we draw another straight line so that it makes same angle of incidence and this straight line will be the reflected ray. we have to make markings to show the direction of propagation of light. This is shown in the following figure.

Similarly when we need to describe the refracction of light, we have to follow the laws of refraction. Due to refraction of light when light travels from optically rarer medium like air to optically denser medium, it deviates its direction and bends towards normal. When light travels from optically denser medium to optically rarer medium it deviates away from normal. Incident ray, refracted ray and emergent ray all are in one plane. angle of incidence is the angle between incident ray and normal. Angle of refraction is the angle between refracted ray and normal. All these concepts are described in following ray diagram.