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12th Grade > Physics

OPTICAL INSTRUMENTS AND SOME NATURAL PHENOMENA MCQs

Total Questions : 30 | Page 1 of 3 pages
Question 1. Image formed on the retina is  
  1.    Real and inverted  
  2.    Virtual and erect  
  3.    Real and erect  
  4.    Virtual and inverted
 Discuss Question
Answer: Option A. -> Real and inverted  
:
A
Image formed at retina is real and inverted.
Question 2. The diameter of the moon is 3.5×103km and its distance from the earth is 3.8×105km. If it is seen through a telescope whose focal length for objective and eye lens are 4 m and 10 cm respectively, then the angle subtended by the image of the moon on the eye will be approximately 
  1.    15∘
  2.    20∘
  3.    30∘
  4.    35∘
 Discuss Question
Answer: Option B. -> 20∘
:
B
The angle subtended by the moon on the objective of telescope α=3.5×1033.8×105=3.53.8×102rad.
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=βα40010=βαβ=40αβ=40×3.5×1033.8×105×180π=20 (approx).
Question 3. For the myopic eye, the defect is cured by  
 
[CPMT 1990; KCET (Engg.) 2000]
  1.    Convex lens 
  2.    Concave lens  
  3.    Cylindrical lens 
  4.    Toric lens  
 Discuss Question
Answer: Option B. -> Concave lens  
:
B
For The Myopic Eye, The Defect Is Cured By    [CPMT 1990;...
Question 4. In a compound microscope, if the objective produces an image Io and the eye piece produces an image Ie, then
  1.    Io is virtual but Ie is real   
  2.    Io is real but Ie is virtual  
  3.    Io and Ie are both real   
  4.    Io and Ie are both virtual  
 Discuss Question
Answer: Option B. -> Io is real but Ie is virtual  
:
B
In a compound microscope, objective forms real image while an eye piece forms a virtual image.
Question 5. The magnifying power of a microscope with an objective of 5 mm focal length is 400. The length of its tube is 20 cm. Then the focal length of the eye-piece is          [MP PMT 1991]
  1.    200 cm
  2.    160 cm   
  3.    2.5 cm
  4.    0.1 cm   
 Discuss Question
Answer: Option C. -> 2.5 cm
:
C
The Magnifying Power Of A Microscope With An Objective Of 5 ...
Question 6. Lens used to remove long-sightedness (hypermetropia) is
 
  1.    Concave lens  
  2.    Plano-concave lens  
  3.    Convexo-concave lens 
  4.    Convex lens  
 Discuss Question
Answer: Option D. -> Convex lens  
:
D
Lens Used To Remove Long-sightedness (hypermetropia) Is  
Question 7. The focal length of objective and eye lens of a microscope are 4 cm and 8 cm respectively. If the least distance of distinct vision is 24 cm and object distance is 4.5 cm from the objective lens, then the magnifying power of the microscope will be
  1.    18 
  2.    32
  3.    64
  4.    20
 Discuss Question
Answer: Option B. -> 32
:
B
The Focal Length Of Objective And Eye Lens Of A Microscope A...
Question 8. If the focal length of the objective lens and the eye lens are 4 mm and 25 mm respectively in a compound microscope. The length of the tube is 16 cm. Find its magnifying power for relaxed eye position
  1.    32.75 
  2.    327.5 
  3.    0.3275
  4.    None of the above
 Discuss Question
Answer: Option B. -> 327.5 
:
B
The image distance for the objective, in this case, is Lf0fe as the focal lengths are not negligible compared to the length of the telescope.
By using m=(Lf0fe)Df0fe
=(160.42.5)×250.4×2.5=327.5
Question 9. For which of the following colour, the magnifying power of a microscope will be maximum  
  1.    White colour  
  2.    Red colour  
  3.    Violet colour  
  4.    Yellow colour  
 Discuss Question
Answer: Option C. -> Violet colour  
:
C
For Which Of The Following Colour, The Magnifying Power Of A...
Question 10. Focal length of the objective and eyelenses of a telescope are 200 cm and 5 cm.  The maximum magnifying power of the telescope is
  1.    40
  2.    48
  3.    60
  4.    100
 Discuss Question
Answer: Option B. -> 48
:
B
m=f0fe[1+feD]m=2005[1+525]=40[1+15]=40×65=8×6m=48

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