Optical Instruments PYQs Set 1 (PDF)

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Mere Teacher · Previous Year Questions NEET Physics · Optical Instruments · Set 1 (Q1-30)
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1. $The magnifying power of a telescope with tube length 60 cm is 5 . Then the focal length of its eye piece is$ (1) $20 cm$ (2) $40 cm$ (3) $30 cm$ (4) $10 cm$ 2. $A compound microscope is a magnification of 24. The focal length of the eyepiece is 5 cm . The final image is formed at the least distance of distinct vision. The magnification produced by the objective is$ (1) $5$ (2) $7$ (3) $4$ (4) $6$ 3. $The magnifying power of a telescope with tube length 60 cm is 5. What is the focal length of its eye piece?$ (1) $30 cm$ (2) $10 cm$ (3) $40 cm$ (4) $20 cm$ 4. $In normal adjustment, for a refracting telescope, the distance between objective and eye piece is 30 cm. The focal length of the objective, when the angular magnification of the telescope is 2, will be:$ (1) $20 cm$ (2) $30cm$ (3) $10cm$ (4) $15cm$ 5. $A astronomical telescope has objective and eyepiece of focal lengths 40 cm and 4 cm respectively To view an object 200 cm away from the objective, the lenses must be separated by a distance$ (1) $50.0 cm$ (2) $54.0 cm$ (3) $37.3 cm$ (4) $46.0 cm.$ 6. $The angular resolution of a 10 cm diameter telescope at a wavelength of 5000 is of the order of$ (1) $1 0^{6} rad$ (2) $1 0^{- 2} rad$ (3) $1 0^{- 4} rad$ (4) $1 0^{- 6} rad.$ 7. $A small telescope has an objective of focal length 140 cm and an eyepiece of focal length 5.0 cm. The magnifying power of telescope for viewing a distant object is [NEET 2024]$ (1) $34$ (2) $28$ (3) $17$ (4) $32$ 8. $The aperture of the objective is 24.4 cm. The resolving power of this telescope. If a light of wavelength 2440 A is used to see the object will be$ (1) $8. 1 x 1 0^{6}$ (2) $10.0 x 1 0^{7}$ (3) $8. 2 x 1 0^{5}$ (4) $1. 0 x 1 0^{- 8}$ 9. $A lens of large focal length and large aperture is best suited as an objective of an astronomical telescope, since [NEET 2021]$ (1) $a large aperture contributes to the quality and visibility of the images$ (2) $a large area of the objective ensures better light gathering power$ (3) $a large aperture provides a better resolution$ (4) $All of the above$ 10. $An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of$ (1) $small focal length and large diameter$ (2) $large focal length and small diameter$ (3) $large focal length and large diameter$ (4) $small focal length and small diameter.$ 11. $In a reflecting telescope, a secondary mirror is used to:$ (1) $reduce the problem of mechanical support$ (2) $make chromatic aberration zero$ (3) $move the eyepiece outside the telescopic tube$ (4) $remove spherical aberration$ 12. $A microscope is focussed on a mark on a piece of paper and then a slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again?.$ (1) $2 cm upward$ (2) $1 cm upward$ (3) $4.5 cm downward$ (4) $1 cm downward.$ 13. $A microscope is having objective of focal length 1 cm and eyepiece of focal length 6 cm . If tube length is 30 cm and image is formed at the least distance of distinct vision, what is the magnification produced by the microscope ? Take D = 25 cm .$ (1) $25$ (2) $6$ (3) $125$ (4) $150$ 14. $If we need a magnification of 375 from a compound microscope of tube length 150 mm and an objective of focal length 5 mm, the focal length of the eye-piece, should be close to:$ (1) $2 mm$ (2) $22 mm$ (3) $12 mm$ (4) $33 mm$ 15. $The magnifying power of a telescope is 9. When it is adjusted for parallel rays the distance between the objective and eyepiece is 20 cm. The focal length of lenses are :$ (1) $10 cm, 10 cm$ (2) $15 cm, 5 cm$ (3) $18 cm, 2 cm$ (4) $11 cm, 9 cm$ 16. $A telescope has magnifying power 5 and length of tube is 60 cm then the focal length of eye piece is$ (1) $10 cm$ (2) $20 cm$ (3) $30 cm$ (4) $40 cm$ 17. $The diameter of moon is 3.5 \times 1 0^{3} k m and its distance from the earth is 3.8 \times 1 0^{5} k m . If it is seen through a telescope whose focal length for objective and eye lens are 4 m and 10 cm respectively, then the angle subtended by the moon on the eye will be approximately$ (1) $1 5^{0}$ (2) $2 0^{0}$ (3) $3 0^{0}$ (4) $3 5^{0}$ 18. $Diameter of human eye lens is 2 mm. Whatwill be the minimum distance between two points to resolve them, which are situated at a distance of 50 meter from eye. The wavelength of light is 5000 A ˚ (2002)$ (1) $2.32 m$ (2) $4.28 mm$ (3) $1.25 cm$ (4) $12.48 cm.$ 19. $The ratio of resolving powers of an optical microscope for two wavelengths λ_{1} = 4000 A^{\circ} and λ_{2} = 6000 A^{\circ} is$ (1) $9 : 4$ (2) $3 : 2$ (3) $16: 81$ (4) $8: 27.$ 20. $The aperture diameter of a telescope is 5m. The separation between the moon and the earth is 4 \times 1 0^{5} km. With light of wavelength of 5500 Å, the minimum separation between objects on the surface of moon, so that they are just resolved, is close to :$ (1) $600 m$ (2) $20 m$ (3) $200 m$ (4) $60m$ 21. $An astronomical telescope of tenfold angular magnification has a length of 44 cm. The focal length of the objective is$ (1) $44 cm$ (2) $440 cm$ (3) $4 cm$ (4) $40 cm.$ 22. $It the focal length of objective lens is increased then magnifying power of :$ (1) $microscope will increase but that of telescope decrease$ (2) $microscope and telescope both will increase$ (3) $microscope and telescope both will decrease$ (4) $microscope will decrease but that of telescope will increase.$ 23. $A telescope of aperture diameter 5 m is used to observe the moon from the earth. Distance between the moon and earth is 4 \times 10^{5} km . Determine the minimum distance between two points on the moon's surface which can be resolved using this telescope. (Wave length of light is 5893 A ˚).$ (1) $60 m$ (2) $20 m$ (3) $600 m$ (4) $200 m$ 24. $A telescope has an objective lens of 10 cm diameter and is situated at a distance of one kilometre from two objects. The minimum distance between these two objects, which can be resolved by the telescope, when the mean wavelength of light is 5000 A ˚, is of the order of$ (1) $0.5 m$ (2) $5 m$ (3) $5 mm$ (4) $5 cm.$ 25. $An astronomical telescope has objective and eyepiece of focal lengths 40 cm and 4 cm respectively. To view an object 200 cm away from the objective, the lenses must be separated by a distance [NEET 2016]$ (1) $46.0 cm$ (2) $50.0 cm$ (3) $54.0 cm$ (4) $37.3 cm$ 26. $In an astronomical telescope in normal adjustment a straight black line of lenght L is drawn on inside part of objective lens. The eye-piece forms a real image of this line. The length of this image is I. The magnification of the telescope is :$ (1) $\frac{L}{I} -1$ (2) $\frac{L + I}{L - I}$ (3) $\frac{L}{I}$ (4) $\frac{L}{I} + 1$ 27. $A person with normal near point 25 cm using a compound microscope with objective of focal length 8.0 mm and an eye piece of focal length 2.5 cm can bring an object placed at 9.0 mm from the objective in sharp focus. The separation between two lenses and magnification respectively are:$ (1) $9.47 cm, 88$ (2) $3.36 cm, 44$ (3) $6.00 cm, 22$ (4) $7.49 cm, 11$ 28. $If the focal length of objective lens is increased then magnifying power o f$ (1) $microscope will increase but that of telescope decrease.$ (2) $microscope and telescope both will Increase.$ (3) $microscope and telescope both will decrease.$ (4) $microscope will decrease but that of telescope will increase.$ 29. $In an astronomical telescope in normal adjustment a straight black line of length L is drawn on inside part of objective lens. The eye-piece forms a real image of this line. The length of this image is I. The magnification of the telescope is$ (1) $\frac{L}{I} + 1$ (2) $\frac{L}{I} - 1$ (3) $\frac{L + 1}{L - 1}$ (4) $\frac{L}{I}$ 30. $An observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20. To the observer the tree appears:$ (1) $10 times nearer$ (2) $20 times taller$ (3) $20 times nearer$ (4) $10 times taller$