| Date | November 2017 | Marks available | 2 | Reference code | 17N.3.SL.TZ0.9 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 0 |
| Command term | Identify and Explain | Question number | 9 | Adapted from | N/A |
Question
A magnifying glass is constructed from a thin converging lens.
A converging lens can also be used to produce an image of a distant object. The base of the object is positioned on the principal axis of the lens at a distance of 10.0 m from the centre of the lens. The lens has a focal length of 2.0 m.
The object is replaced with an L shape that is positioned 0.30 m vertically above the principal axis as shown. A screen is used to form a focused image of part of the L shape. Two points P and Q on the base of the L shape and R on its top, are indicated on the diagram. Point Q is 10.0 m away from the same lens as used in part (b).
Sketch a ray diagram to show how the magnifying glass produces an upright image.
State the maximum possible distance from an object to the lens in order for the lens to produce an upright image.
Determine the position of the image.
State three characteristics of the image.
On the diagram, draw two rays to locate the point Q′ on the image that corresponds to point Q on the L shape.
Calculate the vertical distance of point Q′ from the principal axis.
A screen is positioned to form a focused image of point Q. State the direction, relative to Q, in which the screen needs to be moved to form a focused imaged of point R.
The screen is now correctly positioned to form a focused image of point R. However, the top of the L shape looks distorted. Identify and explain the reason for this distortion.
Markscheme
with object placed between lens and focus
two rays correctly drawn
Backwards extrapolation of refracted rays can be dashes or solid lines
Do not penalize extrapolated rays which would meet beyond the edge of page
Image need not be shown
«just less than» the focal length or f
\(\frac{1}{{10}} + \frac{1}{v} = \frac{1}{2}\)
v = 2.5 «m»
real, smaller, inverted
All three required — OWTTE
two correct rays coming from Q
locating Q′ below the main axis AND beyond f to the right of lens AND at intercept of rays
Allow any two of the three conventional rays.
OR
2.5 or 10 × 0.3 «m»
«–» 0.075 «m»
towards Q
Accept move to the left
spherical aberration
top of the shape «R» is far from axis so no paraxial rays
For MP2 accept rays far from the centre converge at different points
