Ray diagrams for the convex mirror

If an object is in the front of a convex mirror surface that reflects light, the convex mirror will form the image of the object. If the distance of the object from the convex mirror is known, how to draw the image formation of the object? Suppose an object is in the front of a convex mirror as shown in the figure below.

Ray diagrams for the convex mirror 1The orange line = convex mirror

Blue line = the principal axis

Green arrow = object

R = center of curvature of the convex mirror

f = focus of the convex mirror

Images of objects are obtained by drawing all the rays passing through objects, but this is less practical because there will be many lines representing rays. For simplicity, just a few rays are chosen to represent all the beams of light passing through the object. Since this event involves the reflection of light, the law of reflection of light must be obeyed when drawing the image formation.

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Ray diagram

1 :

Ray diagrams for the convex mirror 2The ray 1 or the light beam 1 that come to the convex mirror are drawn parallel to the principal axis and touch the upper end of the object, then reflected by the convex mirror where the beam of light reflects as if from the focal point (f). The incoming light and reflected light must fulfill the law of reflection of light, where the angle of incidence equals the angle of reflection.

Ray diagrams for the convex mirror 32 :

The ray 2 or light beam 2 that come into the convex mirror are drawn as touch the upper end of the object, and towards the point of intersection of the main axis with the convex mirror, then the beam of light is reflected. The incoming light and reflected light must fulfill the law of reflection of light, where the angle of incidence equals the angle of reflection.

3 :

Ray diagrams for the convex mirror 4The ray 3 or the beam of light 3 coming into the convex mirror are drawn to the center point of the mirror curvature (R) and touch the upper end of the object, then reflected by the convex mirror as if the reflected light beam is from the center of curvature. The reflected light beam coincides with the incoming beam of light. The incoming light and the reflected light must fulfill the law of reflection of light, where the angle of incidence equals the angle of reflection. If the beam of light comes to coincide with the reflected beam of light, the beam of light must be perpendicular (90o) with the surface of the convex mirror.

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The image formation (two rays)

The image formation can be drawn using only two rays, as shown in the figure below. If using two rays, there are three possible images formation.

Ray 1 and ray 2

Ray diagrams for the convex mirror 5

Ray 1 and ray 3

Ray diagrams for the convex mirror 6

Ray 2 and ray 3

Ray diagrams for the convex mirror 7

The figure of the image formation using only two beams of light needs to be also adjusted by the object distance from the convex mirror. If the object distance from the convex mirror as in the figure above, then there are three ways to draw the image formation using only two beams of light. If the object distance from the convex mirror is different as shown in the figure above, for example, the object is between the focal point and the center of curvature; then there is not necessarily three ways to draw the image formation, maybe there are only two ways to draw.

If you draw the image formation by a convex mirror, you can choose one method and do not need to use two or three ways.

The image formation (three rays)

The formation of the image can be drawn using three beams of light or three rays, as shown in the figure below.

Ray diagrams for the convex mirror 8If the object distance from the convex mirror is not as shown in the figure, for example, if the object is between the convex mirror and the focal point, or the object is between the focal point and the center of curvature, then the image formation cannot be draw using three ways as in the figure. There can only be two ways to draw the image formation. Please observe the example image formation by the convex mirror, where the object distance from convex mirrors is different, on the topic of the image formation by the convex mirror.

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