Four double convex lenses, with the following specifications are available.
|
Lens |
Focal length |
Aperture |
|
A |
100 cm |
10 cm |
|
B |
100 cm |
5 cm |
|
C |
10 cm |
2 cm |
|
D |
5 cm |
2 cm |
Which two of the given four lenses should be selected as the objective and eye-piece to construct an astronomical telescope?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Lenses A and D respectively
- Lens A has largest focal length making it suitable for objective.
- Lens D has smallest focal length making it suitable for eyepiece.