1 )
A planet is observed by an astronomical refracting telescope having an
objective of focal length 16 m and an eye piece of focal length 2 cm ?
Solution
: -
Distance between objective and eye piece lens : -
L = F˳ + Fe
= 16 + 0.02 =
16.02 m .
Angular magnification
= F( objective ) / F(
eye piece ) ,
Angular magnification
= F˳ / Fe =
16 / 0.02 = - 16
/ 0.02 ,
F˳ is ( - ve
) and
Fe is ( + ve ) in astronomical telescope .
So ,
the image formed by telescope is inverted .
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2 )
If a lens is cut into two pieces perpendicular to the principal axis and only
one part is used , so the intensity of the image will be : -
A ) increased , B
) decreased ,
C ) remain same , D
) None of these ,
Correct
Answer : - C ) remain same ,
Solution
: -
So
number of rays will remain same because number of rays depend on intensity . So
, intensity will remain same .
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