Unit: Optics
Year: 1993 Question#: 91
Question: Two light rays from a common point are refracted by a lens. A real image is formed when these two refracted rays
(1 ) converge to a single point
(2 ) diverge and appear to come from a single point
(3 ) travel in parallel lines
(4 ) totally reflect inside the lens
What is this question really asking?
Explanation by: David V
[ Return to question menu ]
Answer 1
converge to a single point
CORRECT
The definition of a real image is when two light rays converge to a point. This is done when light rays come from a point outside the focal length of a converging lens (see diagram.)
return to top
Answer 2
diverge and appear to come from a single point
INCORRECT
If the light rays diverge, then they passed through a diverging lens. Diverging lenses always produce virtual images (see diagram.)
return to top Answer 3
travel in parallel lines
INCORRECT
Light rays need to intersect or appear to form an image. If the light rays travel in parallel lines, they will never intersect or appear to intersect. Thus no image of any kind will be formed. return to top
Answer 4
totally reflect inside the lens
INCORRECT
Lenses are designed to refract, not reflect light. In all refractions, there is some reflection, but the primary image comes from the refraction, not the reflection. return to top
What's this question really asking?
This is asking you to recall basic information about images and lens behavior. Namely, that real images result from the convergence of actual rays of light. return to top
