| Date | May 2018 | Marks available | 2 | Reference code | 18M.3.SL.TZ2.9 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Distinguish | Question number | 9 | Adapted from | N/A |
Question
The diagram represents a simple optical astronomical reflecting telescope with the path of some light rays shown.
Identify, with the letter X, the position of the focus of the primary mirror.
This arrangement using the secondary mirror is said to increase the focal length of the primary mirror. State why this is an advantage.
Distinguish between this mounting and the Newtonian mounting.
A radio telescope also has a primary mirror. Identify one difference in the way radiation from this primary mirror is detected.
Markscheme
where the extensions of the reflected rays from the primary mirror would meet, with construction lines
eg:
[1 mark]
greater magnification
[1 mark]
Newtonian mount has
plane/not curved «secondary» mirror
«secondary» mirror at angle/45° to axis
eyepiece at side/at 90° to axis
mount shown is Cassegrain
OWTTE
Accept these marking points in diagram form
[2 marks]
waves collected above mirror/dish
waves collected at the focus of the mirror/dish
waves detected by radio receiver/antenna
waves converted to electrical signals
[1 mark]
