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That passes through the principal focus of the concave mirror
focus
It is reflected back parallel to the principal axis. (apex)
Rays which are parallel to the axis of the concave mirror will converge to the focal point.
If the light approaches the mirror along the normal (perpendicular to the mirror), then it reflectsback in the same direction from which it came.In that event, the angle of reflection is still equal to the angle of incidence . . . they're both zero.
That passes through the principal focus of the concave mirror
focus
It is reflected back parallel to the principal axis. (apex)
true
Rays which are parallel to the axis of the concave mirror will converge to the focal point.
If the light approaches the mirror along the normal (perpendicular to the mirror), then it reflectsback in the same direction from which it came.In that event, the angle of reflection is still equal to the angle of incidence . . . they're both zero.
It is reflected back parallel to the principal axis. (apex)
It is reflected back parallel to the principal axis. (apex)
Well this only occurs if the lens is parabolic. It is just a fundamental feature of a parabola to reflected an incident ray parallel to the principal axis through the focal point. That is why lenses etc are parabolic. I dont know if this answers your question (it probably doesnt) but oh well...
The tendency in case of concave lens would be diverging one. When parallel rays fall one side of the concave lens then due to divergence they appear to come, note down that "they appear to come" from a point on the same side. And this point is named as the virtual focus of the concave lens. Now as a ray passes through this virtual focal point that will be definitely a diverging one. Now due to diverging action of the lens, that ray will be further diverged and that will appear to come from a virtual point on the same side and some what nearer to the concave lens. Hence the image will be virtual and diminished and erect one.
a lens such that a parallel beam of light passing through it is caused to diverge or spread out
a convex lens