Question
(a) Fig. 6.1 is a full scale diagram showing a converging lens, the two principal focuses F1 and F2 and an object PO.
On Fig. 6.1, draw two rays from point O of the object to determine the position of the image. Label the image IJ. Measure the length of the image.
image length = …………………………………………………..
[3]
(b) Ring three descriptions of the image.
diminished magnified real same size
same way up as object upside down compared to object virtual [3]
(c) Fig. 6.2 shows three rays of green light passing through glass blocks. 
Three rays of red light approach the glass blocks on the same paths as the rays of green light.
On Fig. 6.2, draw the paths of these rays of red light to the right of the glass blocks. [2] [Total: 8]
Answer/Explanation
Ans:
(a)
Any two correct rays from
• from O through optical centre (and beyond)
• from O parallel to principal axis to centre line of lens then through F1
• from F2 through O to centreline of lens then parallel to principal axis
rays traced back to intersect AND 2.4 – 3.6 cm
(b)
magnified
same way up as object
virtual
(c)
one ray from each prism refracted towards principal axis
(rays) converge to the right of original convergence on the principal axis