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CAIE IGCSE Physics 3.2.3 Thin lenses Question Bank

Practise ray diagrams, image descriptions, focal length language, and common uses of converging and diverging lenses.

Syllabus
2026–2028
Course
Physics 0625

Exam points

  • complete lens ray diagrams using the principal axis and focal point positions
  • describe lens images as real or virtual, magnified or diminished, and upright or inverted

Covered syllabus points

3.2.3.1—Action of thin converging and thin3.2.3.2—Terms focal length, principal axis and3.2.3.3—Ray diagrams for the formation of a3.2.3.4—Characteristics of an image using the3.2.3.5—A virtual image is formed when3.2.3.6—Ray diagrams for the formation of a3.2.3.7—Use of a single lens as a magnifying3.2.3.8—Use of converging and diverging lenses

3.2.3 Thin lenses question 1

[Maximum number: 1]

Which statement about a thin converging lens is correct?

A

All rays of light refracted by the lens pass through the principal focus.

B

All rays initially parallel to the principal axis of the lens are refracted through the principal focus.

C

The focal length of the lens is the distance between the image and the principal focus.

D

The focal length of the lens is the distance between the object and the image.

3.2.3 Thin lenses question 2

[Maximum number: 7]

Question (a)

(a)

Fig. 6.1 is a full-size diagram of a lens and an image I of an object.

Fig. 6.1

Fig. 6.1

The focal length of the lens is 3.0 cm .

[ 5 ]

Question (i)

(i)

On Fig. 6.1, mark two points with labels F , to show the positions of the principal focuses (focal points) of the lens.

[ 1 ]

Question (ii)

(ii)

On Fig. 6.1, draw two rays from the image I to locate the object. Draw the object and label it O.

[ 3 ]

Question (iii)

(iii)

The object is moved so that it is 6 cm to the left of the lens.

State one characteristic of the image formed when the object is in this position.

[ 1 ]

Question (b)

(b)

Fig. 6.2 shows a simplified diagram of an eye with rays from a near object. The eye needs correction for long-sightedness.

Fig. 6.2

Fig. 6.2

[ 2 ]

Question (i)

(i)

On Fig. 6.2, draw the path of the rays inside the eye to show the effect of long-sightedness.

[ 1 ]

Question (ii)

(ii)

A lens is used to correct the long-sightedness.

Draw a lens suitable for this correction.
lens to correct long-sightedness

[ 1 ]
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