State the relative positions of the principal foci (focal points) of both the objective lens and the eyepiece lens when an astronomical refracting telescope is in normal adjustment.
Which combination of lenses gives the largest angular magnification when used to construct an astronomical telescope in normal adjustment?
| Objective lens: Focal length | Objective lens: Type | Eyepiece lens: Focal length | Eyepiece lens: Type | |
|---|---|---|---|---|
| A | 150 cm150\text{ cm}150 cm | converging | 2.5 cm2.5\text{ cm}2.5 cm | converging |
| B | 150 cm150\text{ cm}150 cm | diverging | 2.5 cm2.5\text{ cm}2.5 cm | converging |
| C | 2.5 cm2.5\text{ cm}2.5 cm | converging | 150 cm150\text{ cm}150 cm | converging |
| D | 2.5 cm2.5\text{ cm}2.5 cm | diverging | 150 cm150\text{ cm}150 cm | converging |
Star P and Star Q are located within the same constellation. Star P appears 630 times brighter than Star Q when viewed from Earth. The apparent magnitude of Star P is 1.41.41.4.
Calculate the apparent magnitude of Star Q.
Star P is just visible to the naked eye of an astronomer whose dark-adapted pupil diameter is 6.0 mm6.0\text{ mm}6.0 mm.
Determine, with the support of a calculation, whether she can observe Star Q using a refracting telescope with an objective lens diameter of 120 mm120\text{ mm}120 mm.
Modern telescopes frequently utilise charge-coupled devices (CCDs) rather than the human eye at the eyepiece. Explain two physical reasons why a CCD significantly improves an astronomer's ability to detect very faint stars.
