An object is placed 0.10 m in front of the lens.

(i) On the diagram, construct rays to locate the image of the object, O. The focal points of the lens are labelled F.

(ii) Explain whether the image in (a)(i) is real or virtual.

The object in (a) is now moved so that it is located 0.40 m from the lens. Calculate

(i) the distance of the image from the lens. 

(ii) the linear magnification.

The refractive index of the glass in the lens is greater for blue wavelengths than for red wavelengths.

The diagram shows two rays of blue light incident on the lens.

On the diagram, sketch the paths of the rays if red light is used instead of blue light.

(i)

any correct ray out of the three shown above;
second ray correct;
image correctly located and labelled;

Accept rays without arrows and solid construction lines back to image.

(ii) virtual because no rays pass through the image / image cannot be formed on a screen;

Mark is for explanation, not for statement that image is virtual.

(i) \(\frac{1}{v} = \frac{1}{{0.20}} - \frac{1}{{0.40}}\left( { = 2.5{{\rm{m}}^{ - 1}}} \right)\);
⇒v=0.40(m)

(ii) \(m =  - \frac{v}{u}\);
m=-1;

the refracted rays converge on the principal axis farther from the lens than for blue;