Label the focal point of the mirror with the letter F.

Sketch two appropriate rays on the diagram to show the formation of the image. Label the image with the letter I.

The upper half of the mirror is blackened so it cannot reflect any light. State the effect of this, if any, on the image.

A concave mirror of radius 3.0 m is used to form the image of the full Moon. The distance from the mirror to the Moon is 3.8 × 10⁸ m and the diameter of the Moon is 3.5 × 10⁶ m.

Determine the diameter of the image of the Moon.

F half-way between C and mirror vertex and on the principal axis ✔

one correct ray ✔

second correct ray that allows the image to be located ✔

image drawn ✔

image will be less bright / dimmer ✔

«image distance is $\frac{1}{v}=\frac{1}{1.5}-\frac{1}{3.8\times {10}^8}$ ie» v = 1.5 «m»  ✔ 

$m=-\frac{1.5}{3.8\times {10}^8}$  ✔

image diameter is $\frac{1.5}{3.8\times {10}^8}$ × 3.5 × 10⁶ = 1.4 «cm» ✔

Award [3] for bald correct answer.

Concave mirror. Most of better candidates well identified the position of the focus of the concave mirror and used appropriate rays to show the position of the image. This was a straightforward and successful question for many students.

Concave mirror. Most of better candidates well identified the position of the focus of the concave mirror and used appropriate rays to show the position of the image. This was a straightforward and successful question for many students.

Concave mirror. Most of better candidates well identified the position of the focus of the concave mirror and used appropriate rays to show the position of the image. This was a straightforward and successful question for many students. However in part (iii) many candidates experienced difficulties in understanding image formation. The typical response includes “no image will be produced when a part of the mirror is blackened” as well as “only half of the image will be produced”.

Concave mirror. Most of better candidates well identified the position of the focus of the concave mirror and used appropriate rays to show the position of the image. This was a straightforward and successful question for many students. In (b), many correct and clear answers were seen. However, to be expected some made POT, AEr and algebraic mistakes.