Optical Instruments And Some Natural Phenomena(12th Grade > Physics ) Questions and Answers
Explanation:-
Answer: Option B. -> 20∘:
B
The angle subtended by the moon on the objective of telescope α=3.5×1033.8×105=3.53.8×10−2rad.
Let, theangle subtended by the image of the moon on the eye be β. Also, theangle subtended by the moon on the earth, as well as the eye will be very nearly the same.
Therefore m=f0fe=βα⇒40010=βα⇒β=40α⇒β=40×3.5×1033.8×105×180π=20∘ (approx).
Explanation:-
Answer: Option B. -> 327.5:
B
The image distance for the objective, in this case, is L−f0−fe as the focal lengths are not negligible compared to the length of the telescope.
By using m∞=(L−f0−fe)Df0fe
=(16−0.4−2.5)×250.4×2.5=327.5