What happens to light as it passes through a thin lens?
It is refracted.
Cambridge IGCSE (9–1) Physics 0972 (Extended) (2026–2028) · 3.2.3
Revise Cambridge IGCSE (9–1) Physics 0972 (Extended) (2026–2028) specification point 3.2.3, Thin lenses, with free active-recall flashcards. Flip through the set or review every question and answer below.
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What happens to light as it passes through a thin lens?
It is refracted.
What is the principal axis of a thin lens?
The straight line through its optical centre, perpendicular to the lens.
What is the principal focus of a thin lens?
The point on the principal axis where initially parallel rays converge, or from which they appear to diverge, after passing through the lens.
What is the focal length of a thin lens?
The distance from the optical centre to the principal focus.
What does a converging lens do to a beam parallel to its principal axis?
It brings the rays towards the principal focus on the opposite side of the lens.
What does a diverging lens do to a beam parallel to its principal axis?
It spreads the rays so they appear to come from the principal focus on the same side as the incoming light.
In a converging lens ray diagram, what happens to a ray parallel to the principal axis?
It is refracted through the principal focus on the far side of the lens.
In a converging lens ray diagram, what happens to a ray passing through the optical centre?
It continues approximately straight.
How is a point on a real image located using rays from the corresponding object point?
It is where the refracted rays meet.
Where do rays from each object point converge when an object is outside the focal length of a converging lens?
On the opposite side of the lens.
How can a ray diagram be used to determine a real image's position, size and orientation?
Draw the lens, principal axis, focal points and selected rays to scale.
What are the three possible image sizes relative to an object?
Enlarged, the same size, or diminished.
What is the difference between an upright and an inverted image?
An upright image has the same orientation as the object; an inverted image is upside down relative to it.
Where does a real image form?
Where light rays actually converge.
Where does a virtual image form?
Where diverging rays appear to come from when extrapolated backwards; the rays do not actually meet there.
How do real and virtual images differ in whether they can be projected visibly onto a screen?
A real image can be projected onto a screen at the image position; a virtual image cannot.